Carpentry and furniture products consist of various parts, connected in one way or another and for the most part motionless. In some parts of folding and folding furniture, detachable connections are also used.

A part - a bar, a board (plot), a shield - as the primary element of the product, can be made from one piece of wood, from two or more pieces previously glued together, and can also be veneered.

The connection of two or more parts forms a unit - a shield, a frame, a box, which are structural elements of the product. From the interconnected parts and assemblies, a simple carpentry product or an isolated part of it - a combine, an aggregate - is obtained.

Parts are connected to each other by joinery knitting, glue or metal clips.

According to GOST 9330-60 "Wooden parts. Basic connections", the following groups of connections are distinguished:

• by lenght- parts adjoining each other with their ends; this connection is carried out by splicing or building up parts;
• along the edges(rallying) - two or more elements to obtain a wide detail;
• corner end- parts converging at one angle or another to form the majority of structural elements of building and furniture products;
• corner median- connection of elements, one of which either adjoins its end to the middle of the other (abutment), or intersects it at one or another angle (intersection) to form mainly shields;
• box corner(box knitting) - wide elements; such connections are used when assembling boxes, boxes, etc. They can be end and middle (abutments).

The simplest product or part of a complex product (unit) is formed from the conjugated elements, depending on the purpose of which it is selected and method of connecting elements.

Splicing and building. Due to the relatively small length of the joinery parts, which does not exceed the usual length of the used boards and bars, splicing and building-up in joinery works is mainly used in the manufacture of joinery and construction products (handrails, cornices, skirting boards, etc.), as well as when replacing unusable parts of parts new.

Splicing and extension is performed:

1. back to back when the elements are connected to each other by flat-cut ends at a right or oblique angle;
2. overlay half a tree (Fig. 181, a);
3. round thorns, flat and oblique dovetail type (Fig. 181, b);
4. wedge lock(Fig. 181. c).

Joining is used mainly to connect narrow elements in order to obtain a part of a larger width; much less often rallying serves to increase the thickness. The front sides of the product are veneered - pasted over with valuable wood species. When joining, the following methods of joining elements are used:

1. In a smooth glue joint(Fig. 182, a), which consists in the fact that the parts are pressed tightly with the edges to one another and then glued. After that, the parts are placed in special devices (workbenches, clamps, presses), compressed with screws, wedges, etc. and left in a compressed position until the glue dries. When squeezed, excess adhesive is squeezed out along the joint line.
2. On thorns and dowels(Fig. 182, b, c), when nests are cut out or holes are drilled in the edges of tightly planed parts. into which rectangular spikes or round dowels are inserted. The thickness of the studs should not exceed 1/3 of the thickness of the parts to be joined.
3. At a quarter(Fig. 182, d), when at the edges of the parts to be joined, up to half of their thickness and the same width are longitudinal grooves - quarters.
4. Into the tongue(Fig. 182, d), in which in the edge of one part a groove is selected in the middle - a tongue of 1/3 of the thickness, and in the edge of the other, a ridge corresponding to the groove is selected. The crest and groove can be rectangular or trapezoidal ("dovetail").
5. On the rail(Fig. 182, e), which differs from the tongue-and-groove connection in that grooves are selected in the edges of the parts to be joined, into which the rail is revealed.
6. On dowels(Fig. 182, g), consisting in the fact that in the parts to be connected, trapezoidal grooves with a depth of 1/3 of the thickness of the board are chosen tapering upwards and along the length. In the grooves, dowel bars with a beveled edge are driven into the grooves according to the profile of the selected groove. In addition to bringing the elements together, such a connection also serves as a means of protecting the shields from warping.
7. Into the tip(Fig. 182, h, i), which consists in the fact that a bar is glued to the end edge of the shield, processed in the form of a tongue-and-groove ridge of a triangular, rectangular or other profile. This connection is used to protect the boards from warping and to cover the end, which is difficult to finish and finish.

Joining into a smooth glue joint can be performed with both parallel and non-parallel edges of the jointed boards. The last connection is more economical in terms of material consumption, since boards with edges sawn along the runoff of the tree are used, but it is less beautiful and more difficult to perform.

Rallying on thorns and dowels is usually performed without gluing, mainly for joining parts or parts of the product lying on top of one another in order to prevent their displacement. Performing this type of rallying, especially on thorns, presents some difficulties.

Fusion in a quarter, in tongue and groove and on a strip with glue is stronger, rallying in a smooth fugue, as it gives a large bonding area. Racking on a lath is more profitable than in a quarter or in a tongue, because the wood is not consumed to form a quarter or ridge, and the lath itself is usually generated from waste.

The best and most durable type of joining is a trapezoidal tongue-and-groove connection ("sewing"). Making such a connection with a hand tool is extremely difficult and rarely used. For this purpose, special stitching machines are currently used, which are widely used in the production of furniture and packaging. The connection with a trapezoidal tongue can be made with non-parallel edges both in the longitudinal and in the transverse direction, which allows full use of unedged boards with a runway, which gives a significant departure with other methods of joining. The boards are arranged alternately in different directions with the core side and the butt end, which prevents warping of the shield as a whole.

Corner connections. Joining parts at an angle, i.e. knitting corners, is the most common type of joining in carpentry. The forms of these compounds are very varied; they can be divided into two main groups: frame and box.

There are the following ways of corner connections:

1. Overlay(Fig. 183, a), which is the simplest, but at the same time the least strong of all corner joints. At the end of each part to be joined, wood is selected up to half its thickness.
2. Straight frame thorn(Fig. 183, b, c, d), which is the main type of corner connection of various parts in the carpentry industry. Thorn- part of the bar or part is included in nest selected in another bar or part. Shish is usually obtained by processing the end of the bar. In accordance with the required bond strength, which depends on the total area of ​​the glued surfaces, the frame spike is made single, double or triple. The socket into which the spike is inserted is open on one side (blind socket) and on both sides (through socket). A hole that is open on three sides is called eyelet or eyelet... The nest is in the middle part of the bar, and the eyelet is at its end. A through socket is usually made in cases where the product is painted with an opaque paint, but a deaf one when the outer front side must be clean. If it is undesirable to have the end end of the thorn open, then instead of the eyelet, make a deaf socket with darkness, that is, with a narrowed thorn. This hides defects in the manufacture of the socket and increases the strength of the corner joint, since the tenon is clamped on four, and not on two sides, as in the eyelet.
3. Oblique thorn"dovetail" (Fig. 183, e) - the connection is stronger than a straight thorn. The spike and eyelet are not cut parallel to the edges of the bars; the base of the thorn is made equal to 1/3, and the end - 3/5 of the thickness of the bar.
4. On dowels(Fig. 183, e), sometimes called viscous on round plug-in dowels or dowels. This connection is less strong than a spike; however, it is more economical, since it does not require a cleat allowance.
5. On the mustache(Fig. 183, g, h, i), when the ends of the bars are cut off at an oblique angle. Bars of the same or different widths and converging at any angle can be connected to the mustache. To increase the strength of the connection, it is made in a half-tree with a slotted or deaf thorn (on a whisker with a thorn in the back), and sometimes with a plug-in open or secret thorn.

Pruning corner joints in bars with figuratively processed edges (moldings) are performed in two ways: they process a spike connection of a rectangular shape with trimming the figured part to a mustache or perform a spike connection according to the profile of the joined bars. The first method, which is simpler (but gives a less strong connection), is applicable for manual processing, the second is used for machine processing of parts, providing the necessary accuracy.

Nodal joints in products painted with opaque paint are reinforced with wooden nails (pins) driven into drilled holes.

Junction connections(Fig. 184) are a type of corner joints: the end of one bar is adjacent to the middle part of the other. They are overlaid (in half a tree), with a straight and oblique thorn through or semi-secret. Sometimes the abutments are performed on plug-in round thorns (dowels).

Rice. 185. Box corner joints: a - straight open thorn; b - oblique open thorn; c - an open dovetail thorn; d - in the tongue on the plug-in rail; d - into a tongue with an open and closed end; e - on plug-in flat and round thorns; g - with a dovetail thorn in the back; h - with a dovetail thorn in the back; and - on a mustache with a plug-in rail; k - on a mustache with a comb; l - with glue lug

Box corner joints(Fig. 185) boards or shields are widely used in joinery and furniture. They are made with straight and oblique dovetail or frying pan pins. The number of studs depends on the width and thickness of the parts or shields to be joined. There are spikes at the ends of both parts to be joined, and the flap - a part with an eyelet at the edge of the edge - has one more spike than its corresponding adjacent part.

Box connections can be through, deaf, half-blind and deaf with a clean mustache. Through joints are used for parts located inside the product, also on its front sides, if they are covered with plywood or opaque paint. Details that are open on only one side are connected in half, and those open on all sides are connected in half. Box corner joints are also made on plug-in tenons, but such joints are the least strong.

Box connection connections(Fig. 186) are performed with straight through thorns and grooves with a crest: triangular, rectangular, trapezoidal (vnagrad). Grooved joints are used in cases where it is undesirable to have protruding ends on the outside.

Adhesive bonding. In the carpentry and furniture industry, adhesive joints are used relatively widely. The connection by means of glue alone is sufficiently strong, provided there is a proper fit and proper adhesion of the parts.

This method is used not only when joining parts into a shield for a smooth joint, but also for preparing re-glued panels (gluing panels to the face) and stickers of plywood on a frame, veneering and cladding (stickers of plywood and planks of different species) to obtain from thin bars and planks thick parts (coasters, legs, etc.), as well as for gluing small blocks to finished products (moldings, skirting boards, cornices, glazing beads, etc.).

Veneering. Pasting of plain wood with thin planks (facing) and veneering - pasting with sheets (plywood) of more valuable wood is a special type of adhesive connection to improve the appearance of the product and increase its strength.

Depending on the production method, sawn, planed (knife) and peeled plywood are distinguished.

Parts are veneered on one or € two sides; double-sided veneering significantly increases the strength of the product. Plywood is glued in one or two or more layers.

With single-sided veneering, plywood is glued with fibers parallel to the fibers of the base (frame, core or strapping), and with double-sided - mutually perpendicular.

Due to the shrinkage or drying of the glue and warpage of the plywood that dries out after moistening, the base - a board or shield - warps (Fig. 187, a) and a concavity forms on the surface pasted over with plywood. The smaller the ratio of the base thickness to its width, the greater this warpage. Veneering of a well-dried bar, the thickness of which is not less than half the width, does not at all entail warping.

Sticking plywood to the right (core) side of the bar reduces warpage of the base and, by creating a bulge on the right side, you can compensate for the buckling resulting from glue shrinkage and plywood warping.

Double-sided veneering (Fig. 187, b) does not cause warping of the part. In this case, the internal, non-front sides of the part can be pasted over with plywood of simple species, and the front sides with plywood of more valuable species.

Often it is required to veneer bar parts from three or four sides. In this case, plywood is glued on wide edges, and plywood or solid wood lining on narrow ones (Fig. 187, c, d).

The surface to be veneered is properly prepared: knots are drilled out and the holes are filled with wooden plugs; cracks and cracks are sealed with wooden inserts or putty; the surface is precisely cut out. The ends, which usually do not lend themselves well to veneering, are either glued and then (after the glue has dried) cut out with a cinubel, or pasted over with longitudinal sticks.

Plywood for the front and inner layers is cut into pieces of the required length, its edges are jointed and connected (pulled together) into a sheet (set) according to the dimensions of the surface to be pasted.

Plywood screed produced on the table. Sheets are laid out with jointed edges one to another, attached to the table with small nails, the seams and the surface of the plywood at the seams are wide 15 mm grease with glue and apply strips of paper with a width of 15 mm. After the gluing has dried, the nails are pulled out, the set is removed and glued to the shield.

By using the texture of the wood and applying the appropriate arrangement (set) of plywood sheets, you can get a beautiful pattern and give the veneered product an artistic look.

In fig. 188 shows different views of a set of plywood.

According to a given veneering and a set, plywood sheets are prepared.

Face plywood is selected after it has been cut to size (with an allowance) and its edges are planed. The selection is made in one of the following two ways: the sheets cut from the trunk are laid out, turning over every second sheet (as if unfolding the sheets of an open book) or simply shifted without turning over. In the first case, one leaf will turn out to be the core (right) side facing up, and the other leaf will be the sapwood (left) side. In the second case, all the sheets will be facing upward with one side - the heartwood or sapwood - side.

The first method (unfolding) is used for plywood with ductile wood, which is not very susceptible to cracking. Chopped wood (for example, oak) should not be placed on the face with the left (sapwood) side up, since when shrinking, the plywood sheet will warp, bending upwards, while the sheets facing the left side down will press tightly against the base when warping, and in this case cracks will be hardly noticeable. Therefore, the plywood is shifted by chopping wood during the selection, turning all the sheets with the left side to the base.

Connection of elements from different materials. For the production of furniture, in addition to solid wood, chipboards and fibreboards, wood and other plastics, non-ferrous metals, etc. are currently used. The connections of such materials with solid wood differ from the above compounds.

Elements from chipboard and fiberboard, which have a higher moisture sensitivity, lower strength and an ugly surface, are usually combined with valuable wood species. The following connections are used (Fig. 189): pasting of front surfaces with veneer and sliced ​​plywood, width connection on a smooth jointer and on a plug-in rail, corner joints with plug-in slats and dowels, with plug-in pilaster made of wood on a smooth joint and plug-in rail , middle joints for a smooth joint and in tongue and groove, edgebanding with wood. Fastening of the joints is done with resin adhesives, screws and special clips.

Laminates are attached to the wood using carbinol glue or screws and staples.

Connections with screws, clips and nails.Screw connection used in dismountable products, as well as in products subject to moisture, in which the adhesive connection is unreliable. A screw connection is sometimes used to simplify work when gluing or knitting parts is difficult.

Almost all fittings are fastened with screws: hinges, center plates, handles, locks and various decorations, as well as some wooden parts: glazing beads, covers, etc.

Fastening with dowels(fig. 190) is mainly used for fastening finger joints. For fastening parts from soft wood, the pins are made wedge-shaped, with a pointed end and are made from hard rocks; for fastening hard rocks, round pins made of soft wood are used. Thickness of pins from 3 to 12 mm.

The pins are driven into the holes in the glue-assembled and pressed-in joint. Their ends are greased with glue and hammered with hammer blows, while the hard dowel is pressed into the wood of the joint, and the soft dowel is crushed along the hole. With one pin, it is placed in the center of the joint, and with two, each of them is placed at a distance of 1/4 of the diagonal from the inner and outer corners.

Connections on metal clips are becoming more widespread. The braces used are very diverse.

Stitching parts with the help of wavy plates (Fig. 191, a) is that half of the plate is driven (deepened) along the length into one part, and the other half into the other. Most of all, this is applicable when assembling bars into a frame for its subsequent pasting with plywood (hollow board) or when assembling a massive boardboard for the same purpose.

Usovka connection made with a steel plate driven into the parts to be joined (Fig. 191, b).

Rallying on the rings(Fig. 191, c) consists in the fact that for the ring in the parts to be joined, a groove is chosen, into which a special ring is placed, tightening the parts to be joined.

Metal fasteners to strengthen the knitting of wooden parts, they are most often used in the form of a metal square superimposed on top (Fig. 191, d).

Along with metal braces, they use wooden squares, lugs or breadcrumbs (Fig. 191, d), fastened with glue and screws.

It will be useful for novice home craftsmen to learn about the methods of joining wooden parts. We devote a short educational program to this topic, which will describe the main types of joinery joints and rallies with the use of glue, nails, screws or dowels, or without them at all.

Rules for choosing a connection depending on the type of load

The most simple end connections, they are used when it is necessary to build up a part. These joints are best suited to withstand compressive loads, but good resistance to twisting, stretching and bending can be achieved by cutting down specially shaped locks. The standard end connection is trimmed to half the thickness of both parts. The cut can be straight or oblique, if necessary, to prevent bending, stretching or twisting, a thorn or an obtuse angle is cut at the end of each cut, or the cut is made stepwise, forming a kind of "lock".

1 - a straight overlay in a half-tree; 2 - oblique pad; 3 - straight strip with a stepped joint; 4 - half-wood overlay with an oblique joint; 5 - oblique patch lock; 6 - half-wood connection with an oblique thorn

Corner and side joints are used to connect straight parts into a truss or frame. Usually, this part of the structure is a supporting one, so the main loads fall on displacement and compression. If the structure is subjected to the stipulated static load, a rectangular tenon is cut on one of the parts, and a groove or eyelet of appropriate dimensions is cut on the other. If action to break the structure is possible, the tenon and groove are cut in the form of a trapezoid.

Corner joints: 1 - with an open through thorn; 2 - with a deaf closed thorn; 3 - with a through oblique thorn

Overhead cross and T-shaped connections are used, as a rule, for additional connections between critical structural parts. The main load in them is on compression, displacement and rupture. The first two types of loads are eliminated by cutting half a tree or less, followed by aligning the parts. The shoulders of the notches take the main load on themselves, it remains only to secure the connection with screws or overhead brackets. In some cases, a dowel is used to strengthen the connection or a thorn with a wedge is cut out.

1 - cross connection with a half-wood overlay; 2 - cross connection with landing in one socket; 3 - T-shaped connection with a hidden oblique spike; 4 - T-shaped connection with a straight stepped plate

A separate type of connections is box-type. They are intended for joining boards at right angles. Usually, for a box connection, teeth are cut on each board, the width of which is equal to the distance between them. On different boards, the teeth are cut with an offset, so when joining, the corner from the boards looks like one whole. The teeth can also be wedge-shaped, which prevents the angle from breaking in one direction, or they are additionally fastened with glue or nails.

Box corner joints: 1 - with straight through thorns; 2 - with oblique through thorns

How to make a spike connection

To make a spike connection, you need to circle both parts with a marking line on all faces at a distance from the end equal to the width of the connection. On two opposite sides and the end, the body of the thorn is marked with lines, the markings on both parts are completely identical.

The thorn is trimmed from the sides with a hacksaw for a cross-cut and the wood is chipped with a chisel. The width of the stud is made 2-3 mm larger for subsequent precise processing with a knife or chisel. The groove is cut with a hacksaw for longitudinal cutting and chipped with a chisel, also leaving a small allowance for processing. This is followed by fitting, in the process of which the parts are combined and achieve the most snug fit.

With a T-shaped spike connection, a central spike or groove is cut on one of the parts, and an eyelet is hollowed out on the other, or two side cuts are made, depending on the type of the first part. To make the eyelet, a chisel is used, turning the inclined part of the blade into the hole. If the eyelet is not solid, I make the spike 8-10 mm more depth and cut off its end in the form of a deployed wedge. So, when hammering, the spike will open itself, and the part will be firmly seated.

To connect wide parts, you can use the box connection by cutting several pins and grooves. The easiest way to secure a tenon joint is to drill through the tenons and hammer a wooden dowel into the hole (window gusset).

How to splice boards with glue

A very popular method of joining boards and bars is longitudinal and transverse gluing. When joining the boards with the wide side, the end can be even, although in most cases a tongue-and-groove profile is used. A tight fit of the parts is very important so that the adhesive layer is as thin as possible, this is the only way to achieve maximum strength. Sometimes a small amount of cotton fiber is applied to the butt, greased with glue, this improves the quality of the adhesion.

The boards can also be connected in profile, but this will require wedge-shaped toothed cutting of both ends with an offset to the floor of the tooth for different parts. At home, such an operation can be performed using a hand-held router.

For gluing parts, casein glue or high concentration PVA is used; sifted wood flour is added to the adhesive to give strength. The surfaces are covered with glue and kept in air for 3-5 minutes, after which they are placed under oppression or squeezed with clamps. Such a connection turns out to be stronger than the wood itself and never breaks at the joint.

How to weld structural members

For supporting structures, two types of connections are used - extension and articulation. The easiest way to fuse the two pieces together is to make a half-thickness cut with a hacksaw at the same distance from the ends, and then chop off the excess wood with an ax. After matching the two parts, the connection is usually fastened with two overhead strips nailed to the side of the cut. Bonding is also possible, but only with a tight fit of the parts.

The ends cut into half a tree can be brought together at almost any angle, this is the main method of connecting roof trusses. For fastening the parts, an additional tightening bond is required: the bar is applied to the connected parts from the side at a distance of 30-50 cm from the corner and cut in half the thickness at the points of contact, and then the structure is fastened with nails.

Often vertical and inclined structures need support, for example, when connecting a rafter system to floor beams. In this case, a notch is made of the landing nests on the horizontal beam, into which the racks will be inserted. It is very important to observe the angle of inclination and make the undercut by no more than a third of the thickness of the timber.

Connections with ad hoc links

Almost all joinery joints are made with additional reinforcing ties. In the simplest example, the role of such is played by nails or self-tapping screws.

When building up parts, the unit can be strengthened with a through bolt connection, clamps, brackets and wood grouses, or it is simply wrapped with cold-rolled wire. It is enough to fasten the spliced ​​vertical supports with two overhead strips - wooden or metal.

Corner joints are most often fastened with staples, patch plates or corners. In cases where it is necessary to maintain a small mobility of the connection, one through bolt is used, which either stitches across the place of the overlay of the parts, or pulls them in the longitudinal direction with a minimum offset from the overlay.

The attachment point of the special connection must be at least 10 diameters of the fastening element from the edge and must not have any defects. It is important to remember that often the bonds do not provide the overall strength of the connection, but only compensate for the unaccounted load.

The rafter system is the most complex and one of the most critical elements of the house; the comfort and operation time of the structure largely depends on the correctness of its construction. Calculation and design of the rafter system should only be done by experienced builders or engineers with special training.

It is much more difficult to design a wooden truss system than any metal structure. Why? In nature, there are no two boards with exactly the same strength indicators, this parameter is influenced by a lot of factors.

The metal has the same properties, which depend only on the grade of steel. The calculations will be accurate, the error is minimal. With a tree, everything is much more complicated. In order to minimize the risks of destruction of the system, it is necessary to provide a large margin of safety. Most decisions are made directly by the builders on site after assessing the condition of the lumber and taking into account the design features. Practical experience is very important.

Prices for various types of building boards

Construction boards

Why splicing rafters

There are several reasons why you need to splice rafters.

1. Roof length exceeds standard lumber length... The standard length of the boards does not exceed six meters. If the slope is large, then the boards will have to be lengthened.
2. During construction, there are many good boards with a length of 3-4 m... To lower the estimated cost of the building and reduce the amount of unproductive waste, these pieces can be used to make the rafters after splicing them together.

Important. It must be remembered that the strength of spliced ​​rafters is always lower than that of whole ones. You need to try to place the splice as close to the vertical stops as possible.

Splicing methods

There are several methods of splicing, definitely no better or worse. Craftsmen make decisions based on their skills and the specific location of the joint.

Table. Methods for splicing rafters.

Splicing method	Brief description of technology
	It is used on boards with a thickness of at least 35 mm. Quite a complex method, it requires practical experience in performing carpentry work. In terms of strength, the connection is the weakest of all existing ones. The advantage is saving lumber. Practically at construction sites it is used very rarely.
	The length of the rafter legs is increased with a lining. The cover can be wood or metal. If the length of two pieces of boards is insufficient in terms of the parameters of the rafter system, then this method allows them to be increased. The butt joint has the highest flexural strength and is widely used during the construction of various structures.
	Overlap. Two boards are fixed with an overlap. The simplest method, in terms of strength, takes the middle position. Disadvantage - the total length of the two boards must be greater than the design length of the rafter leg.

In this article, we will look at two of the simplest and most reliable splicing methods: butt and overlap. There is no point in touching the oblique cut, it is almost never used due to the large number of shortcomings.

Building code requirements for joining rafters

Inexperienced splicing of rafters along the length can not only sharply reduce their resistance to bending loads, but also cause the complete destruction of the structure. The consequences of this situation are very sad. Building rules provide for certain patterns when choosing the size of fasteners, places for their installation and the length of the plates. The data is taken based on many years of practical experience.

Spliced ​​rafters will be much stronger if you use metal studs instead of nails to connect them. The instruction will help you make an independent calculation of the connection. The advantage of the method is its versatility, with its help it is possible to solve problems not only with lengthening the rafters, but also with building up other elements of the roof. Specialized companies performed rough calculations and collected data in a table, but only the minimum allowable parameters are indicated in it.

1. Diameter and length of studs... In all cases, the diameter of the studs must be ≥ 8 mm. Thinner ones do not have sufficient strength, it is not recommended to use them. Why? In metal joints, the diameter of the studs is calculated for the tensile forces. During tightening, the metal surfaces are pressed against each other so strongly that they are held by friction. In wooden structures, the stud works in bending. Individual boards cannot be pulled together with great force; the pucks fall into the board. In addition, during the change in the relative humidity of the boards, the thickness is changed, due to this, the pulling force is reduced. Bending studs should be oversized. The specific diameter of the stud must be determined by the formula d w = 0.25 × S, where S is the thickness of the board. For example, for a 40 mm thick board, the stud diameter should be 10 mm. Although this is all relatively relative, you need to keep in mind the specific loads, and they depend on many factors.

   

2. Board overlap length... This parameter should always be four times the width of the boards. If the width of the rafters is 30 cm, then the overlap length cannot be less than 1.2 m. We have already mentioned that a specific decision is made by the master, taking into account the condition of the lumber, the angle of inclination of the rafters, the distance between them, the weight of the roofing materials and the climatic zone of the location of the building. All these parameters have a great impact on the stability of the rafter system.

   

3. Stud hole spacing... It is recommended to fix the fasteners at a distance of at least seven diameters of the studs; the distance from the edge of the board should be at least three diameters. These are the minimum indicators, in practice it is recommended to increase them. But it all depends on the width of the board. By increasing the distance from the edge, it is impossible to reduce the distance between the rows of studs too much.

   

   

4. Number of tie rods... There are quite complex formulas, but in practice they are not used. The craftsmen install two rows of pins, taking into account the distance between them, the holes are staggered.

Practical advice. To increase the bending strength of the spliced ​​rafters, the holes of the studs should not be located on the same line, they must be displaced by at least one diameter.

Board splicing

It is much more convenient to do the work on the ground, prepare a flat area. Place bars on the ground - the rafters will have to be cut, you need a clearance for the circular saw. Know the exact length of the rafters before splicing. You need to measure it on the building, use any thin long boards, rope or construction tape. If an error of a few centimeters appears, no problem. When connecting the rafter legs on the roof, this error is eliminated without problems.

Step 1. Lay one board on the blocks, cut the butt off exactly at a right angle. It is better to cut with a hand-held electric circular saw.

Important. Follow the safety instructions, this is a high-speed and very traumatic tool. Never remove the factory guards on the saw blade or disable the electrical overload relays.

Rafter boards are quite heavy, position them during cutting so that they do not pinch the saw blade or break prematurely during cutting. Prepare the second board in the same way. Pay attention that the cut is only at right angles. The ends of the spliced ​​boards should fit snugly against each other over the entire surface, this is necessary to increase the strength of the spliced ​​rafters. The fact is that even if the connection of the studs is loosened, the ends during bending will abut against each other along the entire length of the cut and hold the load. Studs and overhead boards will only keep the structure from creeping along the length.

Step 2. Place two prepared rafter boards next to each other. Prepare the board for the overlay. We have already mentioned that its length should be about four times the width of the board. If the roof slopes have a slight slope, the distance between the rafters is large, and the roof is insulated with mineral wool, then the bending loads increase significantly. Accordingly, the length of the splicing board must be increased.

Step 3. Place the patch on two side-by-side splice boards. Quite often, the thickness and width of the boards, even from the same batch, differ by several millimeters. If you have such a case, then level the boards from the side to which the crate will be nailed.

Practical advice. The science of resistance of materials says that the thinner the material, the greater its resistance to bending along a thin plane. This means that, for example, five boards placed side by side on an edge with a thickness of 1 cm each can withstand a significantly greater load than one board with a thickness of 5 cm. Conclusion - for splicing it is not at all necessary to cut thick expensive materials, you can use several thin pieces of the required length. There are enough such pieces at any construction site.

Step 4. In a checkerboard pattern and at the specified distances, drill holes for the studs. In order for the individual elements not to move during the drilling of the holes, they must be temporarily fixed to each other. Use long and thin self-tapping screws for this purpose; it is not recommended to hammer nails together. They cut or tear the grain of the wood; the strength of the board decreases slightly. Self-tapping screws do not cut the fibers, but push them apart, after unscrewing the boards, they almost completely restore their original strength characteristics.

Step 5. Drill holes, do not line them up, or the boards may crack during use.

You can find recommendations, after drilling holes, to separate the boards and lay jute between them to prevent the appearance of cold bridges. This is not only wasted work, but also harmful. Why? Firstly, no cold bridges appear at the splice points; on the contrary, they have the greatest thickness and, accordingly, the lowest thermal conductivity. But even if they appear, then there will be no negative consequences, this is the roof rafter system, and not a room window or door. Secondly, jute reduces the frictional force between the splicing elements, and this has a very negative effect on their strength. Thirdly, if condensate gets on the material, which is very likely, then moisture will be removed from it for a very long time. There is no need to tell what are the consequences of prolonged contact of wooden structures with moisture.

Step 6. Insert the studs into the prepared holes, put on washers on both sides and tighten them firmly with nuts. It is recommended to tighten until the washers are pressed into the wood. The excess length of the studs can be cut off with a circular grinder with a disc for metal.

All other rafters are spliced ​​in the same way.

Prices for popular models of electric drills

Electric drills

Overlap splicing

This connection is easier to do, but on one condition - the total length of the two boards allows, it must be greater than the length of the rafter leg by the amount of overlap.

If you have low quality sawn timber, then before starting work, it is recommended to spread them out on a flat surface and make an audit. For long sections of spliced ​​rafters, choose straight ones, and use curves for segments. Although it is highly recommended to buy only quality materials for the rafter system, this is not an architectural element of the building that can be saved on.

Step 1. Select the planks and place them on a raised block of beams. If you want, you can align the ends with a circular saw, if you don't want to - do not align. The condition of the ends does not in any way affect the strength of the overlap splice.

Step 2. Lay the boards on top of each other, adjust the length of the joint and the overall size of the rafters.

Practical advice. The boards should lie on top of each other strictly parallel. Due to the fact that the upper one rises above the lower one by the thickness of the material, under it and the bars should be placed supports from the segments. The thickness of the segments should be equal to the thickness of the bottom board.

Step 3. Align the boards along one of the edges and temporarily fasten them with self-tapping screws. Drill holes, install studs, washers and tighten nuts.

Plywood butt splicing

Prices for various types of clamps

Clamps

One of the ways of splicing rafters helps to save boards and rationally use waste of various lumber. In this case, one centimeter thick scraps of sheet plywood are used.

Step 1. Lay the rafter boards evenly on the site, close the ends, pay attention to the parallelism of the side edges. The boards should be extremely uniform in thickness, the ends are cut exactly at right angles.

Step 2. Apply a generous amount of PVA glue to the surface with a brush.

Step 3. Place the prepared piece of plywood on the splice, press it firmly with the clamps. When fixing, make sure that the plywood does not move from its original place.

Step 4. Using long strong self-tapping screws, screw the plywood to the boards in a checkerboard pattern. The length of the self-tapping screws should be 1–2 shorter than the total thickness of the boards and plywood, their ends cannot protrude from the back side. Be sure to place large washers under the self-tapping screws. Before tightening the screws, drill holes in the rafter. Their diameter should be 2-3 mm less than the diameter of the threaded part of the hardware.

Step 5. Turn the board upside down, place it under the ends of the stand, they should not hang in the air. Remove all installed clamps carefully one by one.

Step 6. Cover the surfaces with glue and place a second piece of plywood on top of them. Clamp it again with clamps.

Step 7. Tighten the screws with great effort.

Important. When tightening the self-tapping screws, pay attention so that they do not run against each other. The offset must be at least three centimeters.

Step 8. Remove the clamps. To strengthen the splice assembly, tighten it with through pins. They should be placed in the same way as for ordinary butt-splice.

Practical advice. The holes for the studs should be 0.5–1.0 mm smaller than the stud diameter. There are times when it is impossible to accurately select the diameter of the drill for wood. Then it is recommended to use a drill with a slightly smaller diameter, let the stud enter with a sufficiently large force.

During its hammering, the first few threads are crumpled from strong hammer blows, which makes it very difficult to tighten the nut. To avoid problems, before driving the stud, tighten the nuts, now let the thread on the end be jammed, it is no longer needed. Check if the glue is dry before reinstalling the rafters. In good weather, it takes about 24 hours to completely solidify.

The final touch is the application of glue

Important. If, during the splicing of the rafters along the length of the boards, the nuts were tightened until the washer was sunk into the wood, then this cannot be done with plywood. Carefully control the pressing force, do not damage the plywood veneer.

How to properly hammer nails into the rafters when splicing

It is not always possible and necessary to splicate individual elements of the rafters with the help of pins, sometimes it is easier to do it with ordinary smooth nails. But you need to be able to hammer them correctly, otherwise, over time, the compression force of the boards will significantly decrease. The length of the nail should be 2.5–3 cm longer than the thickness of the rafters at the junction.

How to drive in nails correctly to connect loaded or critical timber structures?

Step 1. Drive the nail into the planks at a slight angle, but not completely. It is necessary that the tip protrude from the back side by about one centimeter.

Step 2. On the back of the rafter, bend the nail at a right angle with a hammer.

Step 3. Drive the nail in about one more centimeter. Bend the end again, the bend angle should already be much less than 90 °. The more you bend it, the more secure the final fixation will be.

Step 4. Now you can drive in the nail head to the very end. Bend the overhang on the back side until the sharp end is fully inserted into the board. Remember that the point where the body of the nail exits and the point where the tip is driven in should not lie on the same line.

This technology completely excludes an independent weakening of the pressing force.

Prices for various types of fasteners for rafters

Fasteners for rafters

It has already been mentioned that the bending strength of the rafters at the splice is always less than that of the whole element. If possible try to place this knot as close as possible to the ridge, Mauerlat or various struts... Such precautions minimize the risks of mechanical destruction of the rafter leg. If for one reason or another there is no such possibility, then it is not recommended to place the stop under the splice at a distance of more than 15% of the leg length from either end.

Never use black self-tapping screws for the connection.... This metal has two significant disadvantages. First, it quickly oxidizes and loses its original strength. The second - the technology of manufacturing such self-tapping screws involves hardening. Hardened self-tapping screws do not stretch when the permissible load is exceeded, but burst. During the operation of the roof, the relative humidity of wooden structures changes, respectively, the thickness of the boards also fluctuates. And this can significantly increase the tensile force of the self-tapping screw, it will not withstand and will crack.

Do not overdo it with the amount of hardware... If there are too many of them, then the holes will significantly reduce the strength of the parts to be joined, as a result, you will get the opposite effect, the build-up will not increase, but will weaken.

Video - Splicing rafters along the length

Connections of timber elements have the task of tying mating building materials, such as edging beams, so that they do not move relative to each other. According to the position and direction of the connected wooden elements, longitudinal joints and corner joints, as well as joints at branches and crossings, are distinguished. Spatial sheet steel connectors and pre-drilled sheet steel cover plates often replace carpentry joints.

Joints that must transmit forces of a certain magnitude and direction, for example compressive forces, are also called joints of the connected wooden elements as rods, for example, compressed rods. Compressed rods, connected at an acute angle, can be connected at notches. Other joints of wooden structures are made by joining the wooden elements with the help of connecting means.

By the type of connecting means, such connections are called nail or bolted, dowel or dowel connections. In wood construction, glued building structures are also used. As they have particular advantages, the use of glued timber structures is of increasing importance.

Longitudinal connections

There are longitudinal connections on supports and longitudinal connections in the span. Above the supports, perpendicular pins are used, a joint "in a paw" and a partially trunnion joint "in a paw" (Fig. 1). To reinforce these joints, flat or round steel construction brackets can be driven in from the top or from the side. Often, wooden elements are joined to the forehead and secured only with construction brackets. If, however, large tensile forces act at the joint, for example at the girders on the roof rafters, then both elements are joined head-on on the support and are connected by side planks or perforated strips of corrosion-protected steel.

Rice. 1. Longitudinal connections

The runs can also be made in the form cantilever-suspended(Gerber runs) or articulated girders... In them, the joint is located in the place determined by the calculation, not far from the support, in which the bending moments are equal to zero and where there are no bending forces (Fig. 2). There the girders are connected with a straight or oblique overlay. The incoming girder is held in place by a screw bolt, also called a hinge bolt. The hinge bolt with washers must take the load from the suspended purlin.

Rice. 2. Longitudinal connections of Gerber girders

Gerber runs with a joint lying on top are impractical, since there is a danger that the runs at the edge of the joint will come off. When the joint is suspended, spitting, there is no danger of separation.

To connect Gerber girders, spatial elements made of steel sheet are also used, which are also called Gerber connecting elements. They are attached with nails along the frontal abutting ends of the purlins (see Fig. 2).

Corner connections

Corner joints are necessary when two logs or beams in a corner are joined at a right or approximately right angle in the same plane. The most commonly used types of joints are notched trunnions, smooth angled foot and compressed foot (Fig. 3). With the help of cut-out pins and smooth corner legs, the ends of the thresholds, girders and rafter legs lying on the supports or protruding cantilevered are connected. Nails or screw bolts can be used to secure the connections. The compressed paw has planes obliquely entering each other. It is especially suitable for joining loaded, fully supported sills.

Rice. 3. Corner connections

Branches

When branching off, a timber suitable at a right or oblique angle in most cases superficially butts with another timber. In normal cases, a joint on the trunnions is used, and in secondary structures also a joint "in the paw" is used. In addition, timber beams can be joined using metal connecting space elements. In trunnion joints, the trunnion thickness is approximately one third of the bar thickness. The trunnions have a length in most cases from 4 to 5 cm. The groove for the trunnion is made 1 cm deeper so that the compression force is transmitted not through the section of the trunnion, but through a large area of ​​the remaining section of the beams.

When arranging trunnions, normal trunnions are distinguished, passing through the entire width of the beam, and protruding(hemp) pins, which are used for connections at the ends of the bars (Fig. 4). If the beams in the joint do not fit at right angles to each other, for example at corner struts, then the trunnion at the brace must be made at right angles to the horizontal (or vertical) structural element (see Fig. 4).

Rice. 4. Connections with trunnions

When installing trunnions in wooden beams and purlins, the trunnion must carry the entire load. It is more advantageous to carry out such compounds using girder shoes made of corrosion-resistant steel (fig. 9). These shoes are fixed with special nails in such a way as to prevent them from skewing and turning relative to the joint. In addition, the cross-section of the beam is not weakened by the trunnion holes.

Cross connections

Wooden beams can intersect in the same plane or with offset planes and be overhead or support. Bars intersecting in one plane can intersect "IN THE PAW" if the weakening of the section does not play any role (Fig. 5). It is advisable to tie intersecting overhead thresholds on the support beams with round dowels (pins) made of solid wood or steel from 10 to 12 cm long (Fig. 6).

Rice. 5. Connection "in the paw"

Rice. 6. Connection with round keys (pins)

The bars joining on the side get good support on the post, if their connection is made "IN PAZ" (Fig. 7). For this, the planes of intersection of both elements are cut to a depth of 1.5 to 2.0 cm. In this case, a non-displaceable connection is obtained, which is fixed with a screw bolt.

Rice. 7. Groove connection

When joining inclined and horizontal beams, as is usually the case when joining rafter legs with girders - thresholds, a cut is made in the rafter leg corresponding to the slope, which is called inset(fig. 8).

Rice. 8. Inset of the rafter leg

The depth of the inset in the rafter legs at a normal section height of 16 to 20 cm is from 2.5 to 3.5 cm. One nail is used for fastening, penetrating the threshold for a length of at least 12 cm, or a special anchor for attaching the rafters to the girders.

Rice. 9. Steel shoe connection

Cuttings

In the case of notches, a compressed rod entering at an acute angle is connected to another bar using one or more force-transmitting planes on its frontal side. According to the number and position of the force-transmitting planes, a frontal cut, a cut with a tooth and a double frontal cut with a tooth are distinguished.

At frontal cut(also called a frontal stop) the receiving bar has a wedge-shaped notch that matches the shape of the end of the compressed rod (Fig. 10). The frontal plane should run at an angle dividing the obtuse outer angle of the cut in half. The fastening bolt must have the same direction, guaranteeing the joint against lateral displacement. To mark the cuts, parallels are drawn at the same distance from the sides of the corner, which must be halved. The connecting line between the point of their intersection and the apex of the obtuse angle will be the bisector of this angle (see Fig. 10). The position of the fastening bolt is obtained if the distance between the bisector and the end of the notch is divided into three parts parallel to the bisector (see Fig. 10).

Rice. 10. Frontal notch

Under the action of the compressive force, the wood lying in front of the frontal part of the compressed rod works on slice(see fig. 10). Since the permissible stress on a cut of wood along the grain is relatively small (0.9 MN / m 2), the plane of the wood in front of the cut edge (cut plane) should be large enough. Since, in addition, cracking due to shrinkage should be taken into account, then, with rare exceptions, the length of the cut plane should not be less than 20 cm.

At reverse or toothed groove the plane of the notch is cut at right angles to the underside of the compressed rod (fig. 11). Due to the fact that due to the eccentric connection in the toothed groove there can be a risk of splitting of the compressed rod, it is necessary that the free end of the groove does not fit snugly against the support rod and a seam is provided between them.

Rice. 11. Serrated notch

Double cut consists, as a rule, of a frontal cut in combination with a toothed cut (Fig. 12). The direction of the cutting planes is the same as for each of the cuttings of this combination. However, the toothed cut in this case must be at least 1 cm deeper in order for its cut plane to be below the cut plane of the frontal cut. The fastening bolt should run parallel to the frontal part of the notch approximately midway between the bisector and the top of the sharp corner of the joint.

Rice. 12. Double cut

Cutting depth t v is limited according to DIN 1052. For this, the abutment angle (a) and the height h of the bar to be cut out (Table 1) are decisive.

Pin and bolt connections

In the case of pin and bolt connections, wooden beams or boards, touching the sides, are connected by cylindrical connecting elements, such as rod dowels, bolts with countersunk heads and nuts, ordinary bolts with nuts. These rod dowels and bolts must prevent the timber elements from sliding in the joint plane, also called the shear plane. In this case, forces act perpendicular to the axis of the rod dowel or bolt. The dowels and bolts are bending at the same time. In the jointed timber elements, all efforts are concentrated on the inner surface of the dowel or bolt holes.

The number of rod dowels and bolts installed at the junction depends on the magnitude of the transmitted force. In this case, as a rule, at least two such elements should be installed (Fig. 13).

Rice. 13. Connection with rod dowels

In one connection, many shear planes can be located next to each other. According to the number of shear planes, which are connected by the same connecting elements, single-shear, double-shear and multi-shear dowel and bolt connections are distinguished (Fig. 14). According to DIN 1052, single-shear load-bearing connections with rod dowels must have at least four rod dowels.

Rice. 14. Bolted connections

For bolted connections, bolts with nuts made of steel with a standard diameter of 12, 16, 20 and 24 mm are mainly used. To prevent the head and nut of the bolt from cutting into the wood, strong steel washers should be placed under them. The minimum dimensions of these washers are given for the different bolt diameters in DIN 1052 (table 2).

In order to prevent splitting of the timber elements to be connected by rod dowels and bolts, these connecting means must be installed minimum distances between themselves, as well as from the loaded and unloaded ends. The minimum distances depend on the direction of force, on the direction of the wood grain and on the diameter of the dowel or bolt db and do (fig. 15 and 16). Bearing bolts with nuts must maintain greater distances between themselves and from the loaded end than in the case of rod dowels and bolts with hidden heads. On the other hand, rod dowels or bolts with hidden heads that are close to each other in the direction of the wood grain should be spaced apart relative to the cut line so that the joints do not crack (see Fig. 15).

Rice. 15. Minimum distances in the case of rod dowels and concealed head screws

Rice. 16. Minimum distances in the case of bearing bolts

Holes for pins and bolts are pre-drilled perpendicular to the shear plane. For this, electric drills with a parallel movement bed are used. For pins when drilling holes in wood, and when drilling holes in wood and metal connectors at the same time, the hole diameter must match the diameter of the pin.

Also, the bolt holes should match the bolt diameter well. The hole diameter must not be increased by more than 1 mm compared to the bolt diameter. With bolted connections, it is bad when the bolt sits loosely in the hole. It is also bad if, due to the shrinkage of the wood, the bolt clamp in the hole gradually weakens. In this case, a backlash occurs in the shear plane, which leads to even greater pressure of the bolt rod on the boundary planes of the walls of the holes (Fig. 17). Due to the associated flexibility, bolted connections cannot be applied indefinitely. For simple structures such as sheds and sheds, as well as forests, they can, however, be used. In any case, in the finished structure, the bolts must be tightened repeatedly during operation.

Rice. 17. Backlash when bolted

Dowel connections

Dowels are hardwood or metal fasteners that are used together with bolts to connect smooth-jointed wooden elements (fig. 18). They are positioned in such a way that they act evenly on the surface of the elements to be joined. In this case, the transfer of forces is carried out only through the dowels, while the bolts provide a clamping effect in the connection so that the dowels cannot tip over. The laths made of flat or profile steel are also attached to the wooden elements using dowels. To do this, use one-sided dowels or flat steel dowels. Dowels come in various shapes and types.

Rice. 18. Connection of wooden elements using dowels and bolts

When installing dowel joints with pressed dowels, first, holes for bolts are drilled in the connected elements. After that, the wooden elements are separated again and, if necessary, a groove is cut out for the main plate. Depending on the construction technology, the dowel is fully or partially driven into the groove of one of the connected elements using a mallet. For the final clamping of a precisely aligned connection, special clamping bolts with a large washer are used. Connections with many or large press-in dowels are clamped using a hydraulic press. When connecting with a large number of dowels, as is the case when making corner joints in frames made of glued board elements, it is more preferable to use round plug-in dowels, since with pressed dowels the pressing pressure may be too high (Fig. 19).

Rice. 19. Dowel joint in the corner of the frame

Each dowel, as a rule, must correspond to one bolt with nut, the diameter of which depends on the size of the dowel (Table 3). The size of the washer is the same as for bolted connections. Larger or smaller dowels can be used depending on the amount of force acting on the connection. The most common diameters are from 50 to 165 mm. In the drawings, the size of the dowels is indicated by symbols (Table 4).

Table 3. Minimum dimensions in dowel connections
Outside diameter d d in mm	Bolt diameter d b in mm	Distance between dowels / distance from the dowel to the end of the element, e db, in mm
50	M12	120
65	М16	140
85	M20	170
95	M24	200
115	M24	230
The values ​​are valid for the D-type round press-in dowel family.

Table 4. Drawing symbols for special dowels
Symbol	Dowel size
	from 40 to 55 mm
	from 56 to 70 mm
	from 71 to 85 mm
	from 86 to 100 mm
	Nominal dimensions> 100 mm

At placement of dowels it is necessary to adhere to certain distances of the dowels between themselves and from the edges of the wooden elements. These minimum distances according to DIN 1052 depend on the type of anchor and on its diameter (see table 3).

Bolts with dowel nuts are almost always guided through the center of the dowel. Only with rectangular and flat steel dowels do they lie outside the plane of the dowel. When tightening the nuts on the bolts, the washers should cut about 1 mm into the wood. For dowel connections, the bolted nuts must be re-tightened a few months after installation in order for their tightening effect to remain even after the wood has shrunk. They talk about a connection with a constant transmission of force.

Load bearing stud connections

Bearing dowel (nail) connections have the task of transmitting tensile and compressive forces. With the help of dowel joints, load-bearing parts can be fastened, for example, for freely supported trusses, as well as structures made of boards and beams. Stud connections can be made with single-shear, double-shear and multi-shear. In this case, the size of the nails must correspond to the thickness of the lumber and the depth of driving. In addition, when placing the nails, certain distances between them must be maintained. In bearing stud connections, holes must be drilled in advance. The drilled hole should be slightly smaller than the diameter of the nail. Since the wood does not crack so much, the nails can be placed closer to each other in this way. In addition, the bearing capacity of the nail joint will increase and the thickness of the wood can be reduced.

Single shear dowel connections used when compressed and stretched rods from boards or beams must be attached to the beams (Fig. 20). In this case, the nails pass only through one connecting seam. They are loaded there perpendicular to the bore shaft and can bend if too much force is applied. Since shear forces also arise in the connecting seam in the body of the nail, this section plane is called the cut plane. In the case of paired connection of plank rods on the planes of the main beam, there are two single-shear dowel joints opposite each other.

Rice. 20. Single shear stud connection

At double shear dowel joints the nails pass through three pieces of wood to be joined (fig. 21). Nails have two shear planes, since they are loaded in both connecting seams with an equally directed force. Therefore, the bearing capacity of a double-shear-loaded nail is twice that of a single-shear one. In order for the double-shear dowel connections to not disperse, half of the nails are hammered on one side, and the other half on the other. Double-shear dowel joints are mainly used if the free-standing trusses consist entirely or predominantly of boards or beams.

Rice. 21. Double shear stud connection

Minimum thicknesses of timber and minimum nailing depth

Since thin wooden elements break easily when hammering in nails, boards for load-bearing rods, belts and planks must be at least 24 mm thick. When using nails from size 42/110, use even larger minimum thicknessesa(fig. 22). They depend on the diameter of the nail. With pre-drilled dowel joints, the minimum wood thicknesses can be reduced than with simple nailing, as there is less risk of cracking.

Rice. 22. Minimum thickness and depth of driving

Removing the tip of the nail from the closest cutting plane is called the driving depth. s(see fig. 22). It depends on the diameter of the nail dn and has a different value for single-cut and double-cut nail connections. Single shear loaded nails must have a driving depth of at least 12d n. However, for certain special nails, a driving depth of 8d n is sufficient due to the higher holding force due to the special profiling. With double shear connections, a driving depth of 8d n is also sufficient. At a shallower driving depth, the bearing capacity of the nails decreases. If the nails have a driving depth of less than half the required, then they cannot be taken into account for the transfer of forces.

Minimum distance between nails

Fastening of formwork, battens and filly, as well as rafters, battens, etc. acceptable with less than four nails. However, in general, at least four nails are required for each seam or multi-cut nail joint designed to transmit forces.

The uniform arrangement of these nails on the plane of the connection is made using nail marks(fig. 23). So that two nails located one behind the other do not sit on the same fiber, they are shifted relative to the point of intersection of mutually perpendicular nail marks by the thickness of the nail in both directions. In addition, the minimum distances must be observed. They depend on whether the direction of force is parallel or across the fibers. Next, you need to monitor whether the ends of the rods or the edges of the wood will be loaded by the force acting in the joint or not. Since there is a risk of cracking with loaded rod ends or edges, large distances from the edges to the nails must be maintained.

Rice. 23. The minimum distance between nails with a single shear connection

At single shear nail connection vertical or diagonal tensioned bar with nails with a diameter of d n ≤ 4.2 mm, the minimum distances shown in fig. 23. When using nails with a diameter d n> 4.2 mm, these distances should be slightly increased. If the nail holes are pre-drilled, then in most cases smaller distances are required.

At double shear nail connections nails are arranged in ledges. Between the risks of a single-shear nail connection, additional risks are drawn with a minimum distance of 10d n (Fig. 24).

Rice. 24. The minimum distance between nails with a double shear connection

Device of nail connections

When making nail connections, nails must be driven vertically into the wood. In this case, the head of the nail should only be slightly pressed into the wood so that the wood fibers at the junction are not damaged. For the same reason, the protruding ends of the nails can only be bent in a special way. This should only happen perpendicular to the fibers. To apply the location of the nails, as a rule, appropriately drilled templates made of thin plywood or tin are used. In the case of plywood templates, the holes are made of such a diameter that the heads of the nails can pass through them. In the case of templates made of tin, the locations of the nails are marked with a brush and paint.

Nail connections with steel plates

Nail connections with steel strips can be divided into three types, namely, joints with embedded or externally lying plates with a thickness of at least 2 mm and connections with embedded plates less than 2 mm thick.

Outside overlays usually have pre-drilled holes (fig. 25). They are applied over the joint of the beams or boards at the end and nailed with the appropriate number of wire or special nails. At embedded linings with a thickness of at least 2 mm nail holes must be drilled simultaneously in the wood elements and in the lining. In this case, the diameter of the holes must correspond to the diameter of the nail. Embedded linings less than 2 mm, of which there may be several at the joint, can be pierced with nails without preliminary drilling (Fig. 26). Such connections may only be made with specially designed spline tools and only with special approval from the authorities.

Rice. 25. Connection by means of a perforated steel plate-lining

Rice. 26. Nail connection with embedded steel linings (Greim)

Connections with nail gussets

Nail gussets are used for the rational manufacture of wooden half-timbered trusses from single-row sections of wood (Fig. 27). For this, wooden rods of the same thickness are cut to length, impregnated and fitted exactly to each other.

Rice. 27. Connection with a nail gusset

In this case, the moisture content of the wood should not exceed 20%, and the difference in thickness should not be more than 1 mm. In addition, the rods should not have any cuts or edges.

The nail gussets must be positioned symmetrically on both sides and, using a suitable press, press into the wood so that the nails sit in the wood for their entire length. Hammering the nail gusset with a hammer or the like is not permitted.

The fastening with the help of nail gussets creates at the nodal points a connection or joints that are strong in compression, tension and shear without weakening the load-bearing section of the wood. For the transfer of forces, the working area of ​​the connection of the nail gusset is of prime importance (Fig. 28). It corresponds to the contact area of ​​the nail gusset with the wood, with the exception of the edge strip with a minimum width of 10 mm.

Rice. 28. Working area of ​​the connection at the nail gusset

Trusses with connecting rods with gussets are industrially manufactured only by licensed enterprises, delivered ready-made to the construction site and installed there.

In addition to processing solid pieces of wood, it is often necessary to combine wooden parts into knots and structures. Connections of elements of wooden structures are called landings. Joints in timber structures are defined by five types of fits: tight, tight, sliding, loose, and very loose.

Nodes - these are parts of structures at the joints of parts. Connections of wooden structures are divided into types: end, side, corner T-shaped, cruciform, corner L-shaped and box corner joints.

Joinery connections have over 200 options. Only the connections that joiners and carpenters use in practice are considered here.

End connection (extension) - connection of parts along the length, when one element is a continuation of the other. Such connections are smooth, serrated with spikes. Additionally, they are fixed with glue, screws, overlays. Horizontal end connections withstand compressive, tensile, and bending loads (Figure 1-5). Lumber is built up in length, forming at the ends vertical and horizontal toothed joints (wedge lock) (Fig. 6). Such joints do not need to be under pressure during the entire bonding process, as significant frictional forces act here. Milled sawn timber toothed joints meet the first class of accuracy.

The joints of wooden structures must be made carefully, in accordance with three classes of accuracy. The first class is designed for high quality measuring tools, the second class is for furniture products, and the third is for building parts, agricultural implements and packaging. Lateral connection by the edge of several boards or laths is called rallying (Fig. 7). Such connections are used in the construction of floors, gates, carpentry doors, etc. Plank and rack panels are additionally reinforced with crossbars and tips. When covering ceilings and walls, the upper boards overlap the lower ones by 1/5 - 1/4 of the width. The outer walls are sheathed with horizontally laid overlapping boards (Fig. 7, g). The upper board overlaps the lower one by 1/5 - 1/4 of the width, which ensures the drainage of atmospheric precipitation. The connection of the end of the part with the middle part of the other forms a T-shaped connection of the parts. Such connections have a large number of variants, two of which are shown in Fig. 8. These connections (knitting) are used when joining the lag of floors and partitions with the harness of the house. The connection of parts at a right or oblique angle is called a cruciform connection. This connection has one or two grooves (Fig. 3.9). Cruciform connections are used in roof and truss structures.

Rice. 1. End connections of beams that resist compression: a - with a straight overlay in a half-wood; b - with an oblique overlay (on the "mustache"); c - with a straight overlay in a half-tree with a joint at an obtuse angle; d - with an oblique lining with a spike joint.

Rice. 2. End connections of the beams (build-up) that resist stretching: a - in a straight laid on lock; b - in an oblique patch lock; c - with a straight overlay in a half-tree with a joint in an oblique thorn (in a dovetail).

Rice. 3. The end connections of the bending resisting beams: a - with a straight overlay in a half-wood with an oblique joint; b - with a straight overlay in a half-tree with a stepped joint; c - in an oblique patch lock with wedges and a thorn joint.

Rice. 4. Splice joint with reinforcement wedges and bolts.

Rice. 5. End joints of the bars, working in compression: a - butt-end with a secret hollowed-out spike; b - end-to-end with a hidden plug-in thorn; c - with a straight overlay in half a tree (the connection can be bolted); g-with a straight overlay in a half-tree with wire fixing; d - with a straight overlay in a half-tree with fastening with metal clips (clamps); e - with an oblique pad (on the "mustache") with fastening with metal clips; g - with an oblique pad and bolting; h - marking of the slanting lining; and - end-to-end with a hidden tetrahedral spike.

Rice. 6. End augmentation of the milling scheme for end gluing of workpieces: a - vertical (along the width of the part), toothed (wedge-shaped) connection; b - horizontal (along the thickness of the part), toothed (wedge-shaped) connection; c - milling a gear connection; d - sawing out the toothed joint; d - milling of the gear joint; e - connection to the end and gluing.

Rice. 7. Planks rallying: a - on a smooth joint; b - on a plug-in rail; c - in a quarter; d, e, f - in the groove and ridge (with various shapes of the groove and ridge); w - overlap; h - with a tip in the groove; and - with a quarter tip; k - with overlap.

Rice. 8. T-shaped joints of the bars: a - with a secret oblique thorn (in the paw or in the dovetail); b - with a straight stepped pad.

Rice. 9. Cross joints of bars: a - with a straight overlay in half a tree; b - with a direct overlap of incomplete overlap; c - with landing in one socket

Connections of two parts with ends at right angles are called angular. They have through and non-through thorns, open and laterally, half-way overlapping, half-tree, etc. (Fig. 10). Corner joints (knitting) are used in incorrect window blocks, in the joints of greenhouse frames, etc. A spike connection in the dark has a spike length of at least half the width of the connected part, and the groove depth is 2 - 3 mm longer than the spike length. This is necessary so that the parts to be joined easily mate with each other, and after gluing there is room for excess glue in the spike socket. For door frames, an angular spike joint is used in the dark, and to increase the size of the connected surface, it is semi-dark. Double or triple stud increases the strength of the corner joint. However, the strength of the connection is determined by the quality of its implementation. In the furniture industry, a variety of corner box joints are widely used (Fig. 11). Of these, the simplest is an open end-to-end tenon connection. Before making such a connection, spikes are marked on one end of the board with an awl according to the drawing. By marking the lateral parts of the thorn with a file with fine teeth, they make a cut. Every second cut of the thorn is hollowed out with a chisel. For accurate connection, first sawed and hollowed out the stud slots in one piece. It is placed on the end of another part and crushed. Then they saw through, hollow out and connect the parts, cleaning the connection with a plane, as shown in Fig. eleven.

When connecting parts on a "mustache" (at an angle of 45 °), the angular knitting is fixed with steel inserts, as shown in fig. 12. At the same time, make sure that one half of the insert or clip goes into one part, and the other half into the other. A wedge-shaped steel plate or ring is placed in the milled grooves of the parts to be joined.

The corners of the frames and boxes are connected with a straight open end-to-end spike connection (Figure 3.13, a, b, c). With increased quality requirements (from the outside, the spikes are not visible), angular knitting is performed by an oblique connection in the direction, a groove and a ridge or an oblique connection on a rail, as shown in Fig. 13, d, e, f, g and in Fig. fourteen.

A box structure with horizontal or vertical transverse elements (shelves, partitions) is connected using corner T-shaped joints shown in Fig. 15.

In the connection of the elements of the upper belt of wooden trusses with the lower one, corner cuts are used. When mating the elements of the truss at an angle of 45 ° or less, one cut is made in the lower element (tightening) (Fig. 16, a), at an angle of more than 45 ° - two cuttings (Fig. 16.6). In both cases, the end cut (cut) is perpendicular to the direction of the acting forces.

Additionally, the nodes are secured with a bolt, washer and nut, less often with brackets. Log walls of a house (log house) made of horizontally laid logs in the corners are connected with a cut "in the paw". It can be simple or with an additional spike (paw with a pit). The marking of the cut is performed as follows: the end of the log is cut into a square, to the length of the side of the square (along the log), so that after processing a cube is obtained. The sides of the cube are divided into 8 equal parts. Then 4/8 part is removed from one side from below and from above, and the remaining sides are performed, as shown in Fig. 17. Templates are used to speed up the marking and the accuracy of making the cuts.

Rice. 10. Corner end joints of blanks at right angles: a - with a single opening through a thorn; b - with a single through secret thorn (in the dark); c-with a single deaf (blind) thorn in the dark; d - with a single through semi-secret thorn (semi-dark); d - with a single deaf thorn half-dark; e - with a triple open through thorn; g - in a straight overlay in a half-tree; h - through the dovetail; and - in the eyelets with undercut.

Rice. 11. Box corner joints with straight through thorns: a - cutting out the thorn grooves; b - marking the thorns with an awl; в - connection of a spike with a groove; d - processing with a plane corner joint.

Rice. 12. Corner end connections at right angles, reinforced with metal inserts - buttons: a - 8-shaped insert; b - wedge-shaped plate; in-rings.

Rice. 13. Box corner joints at right angles: a - straight open through thorns; b - oblique open through thorns; c - open through thorns in the dovetail; d - groove on the end-to-end plug-in rail; d - in the groove and comb; e - on plug-in thorns; g - on thorns in a dovetail half-dark.

Rice. 14. Oblique (on "mustache") box connections at right angles: a - oblique thorns in the dark; b - oblique connection to a plug-in rail; in - oblique connection on thorns in the dark; d - oblique connection, reinforced with a triangular strip with glue.

Rice. 15. Straight and oblique connections of workpieces: a - for double connection in oblique groove and ridge; b - on a straight groove and ridge; в - on a triangular groove and a ridge; d - on a straight groove and ridge in the dark; d - on straight through thorns; e - on round plug-in spikes in the dark; g - on a thorn in a dovetail; h - on the groove and ridge, reinforced with nails.

Rice. 16. Nodes in truss elements.

Rice. 17. Conjugation of logs from the walls of a log house: a - simple paw; b - a paw with a wind spike; c - paw markings; 1 - wind spike (pit)

Chiseling and cutting wood

In the simplest connection of wooden parts, a spike and a socket are involved. The nests for the studs, as well as the lugs, are made by chiselling along the markings. Chisels and chisels are used for chiselling. Rectangular nests are hollowed out with chisels, and nests in narrow and thin parts are selected with chisels, spikes and nests are cleaned, connections are adjusted, chamfers are cut. In addition, chisels are used to process curved surfaces in cases where this cannot be done with another tool, such as a plane.

Chisels (Fig. 1) are carpentry and joinery. Chisel handles are made of dry hardwood: beech, hornbeam, maple, ash, etc. The tool must be sharpened; chipping on the blade is not allowed. In the case of a through socket, the workpiece is marked on both sides (Fig. 2, a), in the case of a blind one - from one side (Fig. 2, b). The through-hole is first selected on one side of the workpiece, then on the other.

The chisel is selected according to the width of the nest. For convenience, the same nests are sometimes chosen simultaneously in several parts, folded in a foot. The chisel for work is placed with a chamfer inside the nest, stepping back from the marking line by 1 ... 2 mm (Fig. 2, c). This is necessary to clean the nest with a chisel. During operation, the bit is held perpendicularly. After the first blow to the bit, placed across the fibers, the fibers are cut, after the second blow to the bit, placed inside the socket, chips are separated (Fig. 2, d).

Rice. 1. Chisel: a - carpenter's (blade width - 16, 20, 25 mm); b - carpentry (blade width - 6, 8, 10, 12, 16, 20 mm).

Rice. 2. Chiseling of nests with a chisel: a - through nest; b - blind nest; в - bit position; d - chiseling technique.

Rice. 3. Mallets: a - round; b - prismatic.

Rice. 4. Using an emphasis when chiselling: 1 - clamp; 2 - detail; 3 - metal stop; 4 - chisel.

Rice. 5. Chisels: a - flat (blade width - 4, 6, 8, 10, 12, 16, 20, 25, 32, 40, 50 mm); b - semicircular (blade width - 4, 6, 8, 10, 12, 16, 20, 25, 32, 40 mm).

The shavings must be trimmed to the full depth of the nest - to the chopped fibers, otherwise a nest with even edges will not work. When chiselling the lugs, when the sides of the socket are sawn off, undercutting is performed, that is, the corners of the lug are trimmed for subsequent final chiselling.

Mallets, which hit the tool during chiselling, are round or prismatic (Fig. 3). The wood of elm, hornbeam, viburnum serves as the material for mallets.

When slotting a hole in a thick workpiece, it is recommended to use a stop (Fig. 4), which is a metal strip 1 - 1.5 mm thick, bent at an angle of 90 °. Such an emphasis is attached to the bar with a clamp. In order not to spoil the surface of the part when clamping, it is necessary to put a gasket under the strip.

Chisels (Fig. 5) handle sockets, edges, grooves and chamfers. Curved surfaces are processed with semicircular chisels, all the rest are flat. The angle of sharpening of chisels is 25 °.

Techniques for working with a chisel are shown in Fig. 6. Carrying out cutting with a chisel, with the left hand adjust the thickness of the removed chips and the direction of cutting, and move the chisel with the right hand. In fine details, the nests and lugs are hollowed out with chisels using a mallet; in all other cases, hand pressure is used.

Since the tool has a sharp cutting part, any loss of attention during work inevitably leads to injury, therefore, when working with a chisel, you need extreme care and knowledge of the basic rules for using it. It is forbidden to cut with a chisel towards yourself, with the emphasis of the part on the chest, with the part on the knees, on the weight and in the direction of the supporting hand.

On sale there are forged chisels, which have the best cutting qualities, and stamped. Semicircular chisels with a small cutting width, as well as cranberry chisels, are made, as a rule, by the craftsmen themselves. They are used to pick out wood in round nests when performing simple carvings. These chisels are also found in wood carving tool kits.

For a carpenter's work, it is enough to have two chisels with a blade of 6 and 12 mm wide, as well as a set of chisels with a blade of 2 to 16 and 25, 40 mm wide.

A chisel that cuts wood meets its resistance. The amount of resistance that the cutter encounters on an area of ​​1 m2 of the cross-section of the chip is called the resistivity to cutting. When cutting wood, the angles formed by the front and rear edges of the cutter with the processing surface are distinguished (Fig. 8).

The angle between the front and back edges of the cutter is called the sharpening angle. For planing knives and chisels, it is 20 ... 30 ° and depends on the hardness of the material being processed.

The angle between the leading edge of the cutter and the machining surface is called the cutting angle. For planing knives of hand tools, it is 45 ... 50 °, and machine knives - 45 ... 65 °. The surface finish depends on the value of the cutting angle - the larger it is, the smoother the surface. Increasing the cutting angle increases the cutting force. Surface finish depends on tool speed and material feed. In other words, the faster the tool rotates and the lower the feed rate, the better the surface finish. The angle between the back edge of the cutter and the machining surface is called the clearance angle. The amount of this angle depends on the sharpening angle and the cutting angle.

There are three main types of cutting (Fig. 9): across the fibers, along the fibers and cutting to the end. End cutting requires the most effort. Cutting obliquely (at an angle to the direction of the fibers) is performed with oblique or twisted wood. Cutting along the fibers is 2 ... 2.5 times less than cutting across the fibers.

The cutting force depends not only on the sharpening angle and the cutting angle, but also on the hardness of the wood, the width of the cutter blade, wood moisture, cutting direction, sharpening of the cutter and friction forces against sawdust and shavings.

Hard wood (oak, beech, ash, pear, etc.), as well as wood with knots, curl, oblique, requires great efforts during processing. The inhomogeneity of the wood structure predetermines the unequal resistance value, depending on the cutting direction.

The chip shape depends on the cutting direction. When cutting to the end, the chips will turn out in the form of sawdust. When cutting along the grain, ribbon-like chips are formed. When cutting wood across the grain, shavings are obtained in the form of small chips, and the processed surface becomes rough.

Dulling a cutter requires an increase in cutting force. A blunt cutter does not cut, but presses and tears the wood. Due to the bluntness of the cutter after 4 hours of work, the cutting force increases by 1.5 times. A dull cutter increases the friction between the cutter and the chips, which requires extra effort and overheating of the cutter.

Wet wood is easier to process than dry wood because of the hardness of the latter. However, the cleanliness of the processing of damp wood is lower due to the hairiness.

The wood finish depends on the cutting direction. Cutting along the grain gives a smooth surface. When cutting across the grain, cleanliness is possible with a sharp cutter and very fine chips. The cutter, working on wood, goes deep into it, the chips are separated due to elasticity before the cutter touches, and the processed surface has a roughness. This is typical when cutting across the die (Fig. 10, a). To obtain the cleanliness of the surface treatment, a retaining ruler is placed in front of the cutter. A clean surface can be obtained if the cutter of a planing tool (hand, electrified or machine tool) is supplemented with a chipbreaker (Fig. 10, c, d). It increases the cutting angle, breaks the chips, turning them into a spiral. The thinner the chip thickness, the better the surface finish.

Rice. 9. Cutting wood: a - cutter in open cutting; b - cutter in closed cutting; в - cutting directions; 1 - across the fibers - to the butt; 2 - along the fibers; 3 - in the tangential direction; 4 - in the cross-end direction; 5 - in the longitudinal-end direction; 6 - in the longitudinal-transverse direction.

Rice. 10. Cutting techniques: a - chipping off the chips before they are cut off; b - cutting with a retaining ruler; c - the use of a chipbreaker; d - with an increase in the cutting angle.

An increase in cutters (teeth of a circular saw, knives on the planer shaft, etc.) reduces the thickness of the chips and increases the cleanliness of the processing.The quality of processing of wood of any species, including the presence of defects (knots, oblique, curl, etc.), is affected by the speed of movement incisor. With an increase in the speed of rotation of the cutting tool, the waviness of the chip formation becomes finer, which increases the cleanliness of the processed surface. The cleanliness of processing of individual areas is affected by defects, properties of wood, sharpness of cutters, inaccuracy in marking, violation of technology. Deformations of wood caused by its moisture exceed the size deviations permissible in woodworking. Before processing lumber for carpentry and joinery, the moisture content of the wood is checked.

Additional fasteners for joinery connections

Wooden structures are deformed during operation, their joints become fragile. In such cases, the joints are secured with wooden dowels, thorns (dowels), wedges and dowels (Fig. 1) made of very hard and dry wood (moisture content 4 - 6%).

Wooden nails (pins) made from oak, maple, ash or birch. Before driving the dowel, a hole (through or blind) of the required diameter is drilled and the edges of the dowel are rounded. This protects the wood from cracking at the joints (in the corners of window and greenhouse frames, etc.). Wooden spikes (dowels), for example, secure the rafter joints on the roof ridge. They are cylindrical, rectangular and square. The lower end of the thorn is made somewhat pointed. Before driving the spike, a hole is drilled that is slightly smaller in diameter than the spike diameter. Wooden wedges are made of coniferous wood (pine, spruce), single or double-sided. One-sided wedges have one wide side obliquely cut, and two-sided wedges have both sides. The sides have a slope of 1: 6, 1: 7 and 1: 8 °. With such wedges, they strengthen and stretch wooden structures, level the floor joists, raise the settled parts of the walls and roofs. Wedges are used to wedge the handles of hand tools (axes and hammers), although metal wedges should be preferred.

Keys. Composite beams of two or three beams with wooden dowels. Shear forces between them are absorbed by the dowels. The elements of the beam are additionally pulled together with steel bolts. Oak dowels are inserted into the slots between the composite beam elements. The nests for the dowels are chosen by the electrician simultaneously in two bars, then the dowels are driven into the nests with blows of a wooden hammer. The protruding ends of the keys are cleaned with a plane. The dowels in the middle of the span of the composite beams are not placed due to the low load.
Keys in relation to the connected elements are distinguished: longitudinal, transverse, oblique longitudinal and tension keys (Fig. 2). Cross keys (compared to longitudinal ones) provide a less strong connection, since the wood across the grain has less resistance than along the grain.

Split beams with dowels are made from well-dried wood. If the key is installed in a slot with a clearance, then it will not accept shear forces and the transmitted load will be transferred to other keys. Mechanized production of keys and sockets guarantees the appearance of gaps. The cross-section of polybeams should not be weakened by sockets by more than 1/3 of the element height. With a symmetrical arrangement on opposite sides of the sockets, their depth should not exceed more than 1/6 of the thickness of the element, but not less than 2 cm. Longitudinal keys and bolts are used to connect the bars (Fig. 2, e). A strong and tight connection is obtained using two taper keys with an interference fit (Fig. 2d), acting as wedges. The advantages of such keys are that during the operation of the wedges it is possible to restore the tightness. Dowel joints are used to reinforce floor beams and Derevyagin beams (Fig. 3).

Rice. 1. Installation of plug-in dowels: a - installation of a cylindrical wooden dowel (dowel) on the glue; b - a stressed corner joint on two cylindrical spikes; c - a strained corner joint on three rectangular wooden spikes.

Rice. 2. Tightening by bolts of two beams connected with dowels: a - with longitudinal dowels; 5 - with transverse dowels; h - diagonally located transverse keys; g - wedge-shaped dowels; d - bolts passed through the keys.

Fig 3. Composite beam of the Derevyagin structure: a - front view and cross-section; b - a fragment of the location of the keys in a composite beam.

Manufacturing of panels from wood

To minimize or prevent warping of boards intended for the manufacture of furniture and for other purposes, the following measures are taken: for the manufacture of boards, only dry wood is used (moisture content - 8-10%); wide boards are sawn into narrower ones, and boards are made with a width of no more than 100 mm; adjacent areas in the shields are positioned so that the annual layers at the ends of the joined blanks when joining are at different angles (it is better if they are directed in opposite directions).

To reduce the warping of the wood-block panels from the massif, measures of a constructive nature are also used (Fig. 1): rallying on dowels with tips and tying the panels with a frame with grooves. The best effect is obtained by tying the panels with a frame.

Shields from solid wood are knitted on the crest, dovetail spikes and plug-in round spikes. The easiest way to mark and perform is comb knitting. In this case, the dimensions of the pins are equal to the dimensions of the lugs of the socket. Dovetail stitching is mainly used in the manufacture of boxes, caskets, etc. It is difficult both in marking and in manufacturing.

T-knitting of joinery boards is widespread (Fig. 2). It is performed mainly in a groove and a ridge. At the same time, the edges are carefully processed, since their exact fit is required. The grooves are arranged by hand rallying; their depth is from 1/3 to 1/2 of the thickness of the shield. The easiest to implement is the connection into a wide groove. The use of shoulders increases the stability of the knit. The greatest rigidity of the structure will be when connected to a wag with two shoulders. It is performed mainly without the use of glue. It should be noted that the gratuity method is used only for knitting shields from an array.

In addition to the basic methods of knitting into knots, the parts are also connected with nails, screws and bolts, using metal and wooden squares and an additional bar (Fig. 3).

The glue-wedge connection is considered to be very strong. How to make such a connection is shown in Fig. 4. When the spike with the wedge inserted into it reaches the stop in the bottom of the socket, it will wedge and will be firmly held in the socket. A wedge can be made from solid and dry wood (oak, beech, etc.).

How to drive a nail correctly: First, mark the points and prick them with an awl, keeping an eye on the tilt of the awl, as the nail will go in the direction of the prick. If possible, nail the nail not perpendicular to the plane, but at a slight slope. The connection will be more reliable from this. If the nail is nailed perpendicular to the plane, then it will serve as the axis of rotation and the connection will soon weaken. It is necessary to nail a thin part to a thick one. The diameter of the nail should be no more than 1/4 of the thickness of the pierced part, and its length should be 2 ... 4 times greater than this thickness. Bend the tip of the nail when punching the parts to be joined. To do this, press the triangular file firmly against it and bend the hook with a hammer on the end of the nail. After removing the file, drive the hook into the wood.

To prevent the board from splitting when hammering in a nail, blunt the tip (or bite off with nippers). Such a nail will crush the wood fibers, but will not split it.

Rice. 1. : a - rallying on the key; b - strapping with a frame with a groove; 1 - shield; 2 - socket; 3 - key; 4 - frame with a groove; 5 - comb.

Rice. 2. : a - into a wide groove; b - into a narrow groove with one shoulder; c - into a narrow groove with two shoulders; g - a prize with one shoulder; d - graffiti with two shoulders; e - awarded with flat spikes; g - grants with inserted round spikes.

Rice. 3. : a - with a metal square; b - with a plywood square; in - a wooden block; d - tie bolt.

Rice. 4. : 1 - socket; 2 - wedge; 3 - thorn.

When joining joinery with nails, remember that a nail driven along the grain will hold weaker than a nail driven across it. Several hammered nails close together along the same layer can split the board. This will also happen if a thick nail is hammered near the edge. Therefore, for the strength of the connection, hammer in a few not very thick nails in two rows, placing them in a checkerboard pattern. If, based on the design of the part, you need to hammer in a nail at the edge of the edge, then pre-drill a hole for it. The hole diameter in this case should be 1/5 - 1/7 smaller than the nail diameter.

To hammer a nail at the right angle, especially a small one, stick a piece of plasticine or wax on the place where it should be hammered and stick a nail into it at this angle. After one or two blows with a hammer, the plasticine can be removed.

When nailing a board, do not hammer in the nails parallel to each other, but at a certain angle, and each of them in different directions. The fastening in this case will be more reliable.
You can hammer in a nail in a hard-to-reach place using a metal tube and a rod that fits freely into this tube. To do this, place the tube in the place where the nail should be hammered, lower the nail into it, then the rod and hit the rod several times with a hammer. The nail will go into the wood, but unevenly. After removing the rod, align the position of the nail with a tube and then hammer it in according to the "nail - rod - hammer" system. The rod should be 10-15 mm longer than the tube.

If the screw connecting the parts is loose and turns when screwed, it can be strengthened by first inserting a match into the socket; the screw itself must be lubricated with petroleum jelly. It is difficult to screw a screw into chipboard. But you can do this without much effort if you pre-drill a hole with an electric drill. Fill this hole with glue, place a piece of soft plastic tubing in it and screw in the screw. The glue that has penetrated the inside of the tube will facilitate the screwing process; when dry, it will firmly hold the tube and screw in the socket.

When unscrewing the "stubborn" screw, tap lightly with a hammer on the handle of the screwdriver inserted into its slot. In this case, the screwdriver must be turned with a certain effort.

To properly screw the screw into hard wood, prick the screwing place with an awl and pour some soap crumbs into it; the screw will be easier to screw on. In addition, when screwing in a thick screw, drill a hole 1/5 smaller than the screw diameter; the depth of the hole must be greater than the length of the screw. With a screw diameter of 2 mm or less, there is no need to drill: just make a prick with a sharp object (awl, scribe, etc.).

How to choose a piece of wood

Wooden blanks, called in the common people "linen", come in many different shapes and sizes. They are made mainly from available cheap wood species - linden, birch, aspen. The main rule when choosing a blank is the quality of the material and assembly (for glued products). The wood for the blank (except for solid turned blanks) must be aged - dried, so that after processing and drying the tree does not "lead", it does not crack or dry out, and there must be no visible severe damage, pronounced burrs, scoring and through holes from knots ... The surface should be smooth, not loose or porous.

The assembly quality of glued blanks (boxes, icon boards, complex shapes) affects how the products behave after processing. If the location of the layers is incorrectly selected and the parts are poorly fitted, then gaps may appear at the joints. Do not expect that the crooked box will then "dry up" and align, as unscrupulous sellers promise, rather the opposite.

To make jewelry you need wooden buttons, beads, bracelets. For painting, decoupage and decoration - frames, plates, trays, spoons, nesting dolls, dolls, cup holders, cutting boards, boxes, dishes, vases, caskets, mugs, whistles, toys. Ordinary boards are not suitable for icon painting, special ones are needed - icon ones, with special inserts against warping.

For the "Trekhranka", "Kudrinka", "Tatyanka" carvings, all linden blanks are suitable (birch and aspen are more difficult to handle with cutters) without knots with a wall thickness of 7-10 mm for low relief and 10-15 mm for high relief. And it is better if the workpiece is made of wood of 2-3 year old trees, because it is more homogeneous and dense in structure. There are blanks only for carving, these are gingerbread boards, forms for Easter.

For light decoupage and light tinted carving, the workpieces must be free of darkening. For painting and decoration, darkened blanks are primed, so dark knots and "marble" coloring of wood will not interfere, as well as shallow dents that can be hidden - they are filled with a mixture of sawdust with PVA (in several layers with intermediate drying) or a mixture for papier before priming -mash (it is better to make a mass from pieces of napkins with glue). In the same way, you can correct a defect in collapsible chiseled forms (nesting dolls, apples, eggs, pears) when the upper part sits loosely and falls off when turning over - for this you need to coat the inner edge of the upper half with the mixture and dry well (if done on the lower part, it will be noticeable and ugly). If the hollow collapsible "chisel" has dried out unevenly and does not close, then the upper part is polished from the inside and the outer rim of the lower one.

Before processing, the workpieces should be stored in a tightly closed plastic bag in order to maintain their stabilized moisture content and prevent them from drying out, warping or dampness.

Saws and sawing

Saws and sawing. Saws are made of high quality steel with serrated teeth. For carpentry and joinery work, use a wide hacksaw, a hacksaw with a backing, a narrow hacksaw; a saw with a cutting depth limiter (reward), a bow saw, and a plywood file (knife) (Fig. 1).

A wide hacksaw is made of a steel tape 0.7 m long, 11 cm wide at the handle and 2 ... 7 cm at the narrow end. The handle can be wooden, metal or plastic. A narrow hacksaw is used to cut curved through holes in large parts. The jigsaw (Fig. 2) has a narrow and thin (0.3 mm thick, 1 ... 2 mm wide) file with fine teeth. The file is fixed in an arched frame and can be easily removed. A jigsaw is used to cut thin parts (plywood) of a curved shape. Before starting work, the end of the file is inserted into a pre-made hole, and the other end is fixed in a frame. Sawing is carried out according to the markings. At the end of the work, the end of the file is released and removed from the hole of the part.

Hacksaws with backing are used for shallow sawing, for example, sawing grooves in wide blanks, for fitting parts during their assembly. The top of the blade is reinforced with a steel backing that increases the rigidity of the blade. The fine teeth are in the shape of an isosceles triangle. Saw in both directions with a hacksaw (Fig. 1, c).

By the shape of the teeth, saws are distinguished for longitudinal, mixed and cross cutting (Fig. 3).

Saws with oblique teeth are used for sawing along the grain. They cut wood in one direction - away from themselves. The cavity between the teeth is called a sinus. Tooth pitch is the distance between the tops of adjacent teeth. The height of the tooth is equal to the perpendicular drawn from the top of the tooth to its base. The saw tooth has three edges (Fig. 3, a). In rip saws, the cutting is performed by the short cutting part - the leading edge, and the side edge only separates the wood grain.

Rice. 1. : a - wide hacksaw: b - the same, narrow; c - butt hacksaw; d - award; d - plywood file.
Rice. 2. Jigsaw.	Rice. 3. : a - saw elements; b - the corners of the saw teeth; I - for rip sawing; II - for mixed sawing; III - for cross cutting: 1 - side cutting edges; 2 - front face; 3 - front cutting edge; 4 - step; 5 - top; 6 - sinus; 7 - height; 8 - the line of the base of the teeth.

A bow saw is used for ripping and cross cutting. It consists of a beam frame with a tensioned saw blade. The latter is made of a steel strip about 1 m long, 45 ... 60 wide and 0.4 ... 0.7 mm thick. The pitch of the teeth is 4 ... 5 mm, the height of the teeth is 5 ... 6 mm. The ends of the saw blade are secured to the bottom of the uprights of the beam frame. The canvas is pulled with a string of twine fixed between the upper ends of the struts and twists. The turning of the saw blade is carried out using the handles. This saw can be operated by one person. The cut is smooth and even. Crosscut saw teeth cut the fibers, the side edges of the teeth, and the leading edge only separates them. In rip saws, the leading edge of the tooth cuts wood. This is taken into account when determining the sharpening angles of saw teeth for cross and rip sawing.

Rice. 4. Sawing along the grain with a bow saw if the material is in a horizontal position: to the right - the position of the worker's feet during sawing.
Rice. 5. Supports: a - wooden with a movable support; b - metal with a roller; в - wooden with a roller.	Rice. 6. Sawing with a bow saw along the fibers with vertical fastening of the material: a - the position of the worker's hands during sawing; b - the same, feet.	Rice. 7. Cross cutting: a - cutting techniques; b - supporting the part to be sawn off by hand at the end of the sawing.

For saws for ripping soft wood, the sharpening angle is 40 ... 45 °, for saws for hard wood - up to 70 °, in cross-cut saws, the angle between the cutting edges of the teeth is 60 ... 70 °, and the sharpening angle is 45 ... 80 °. Saws for mixed sawing have a sharpening angle of 50… 60 °. The angles of the saw teeth are as follows: for rip sawing - 60 ... 80 °, for transverse - 90 -120 °, for mixed - 90 °. For sawing shallow grooves and nests of spike joints, a so-called reward is used. To adjust the cutting depth, it has a movable stop. Saw blade thickness 0.4 ... 0.7 mm, length -100 ... 120 mm.

Types and methods of sawing. By the type of fastening of the part in the workbench, they are distinguished: horizontal sawing along the fibers, vertical sawing along the fibers, horizontal sawing across the fibers and sawing at an angle. When cutting horizontally along the fibers, the workpiece is fixed by pressing it to the table with clamps (Fig. 4) so ​​that the sawn-off part protrudes beyond the edge of the workbench. At the same time, the worker's body should be slightly tilted forward, the saw must be held vertically. First, make a gash, moving the saw up several times, after the gash becomes deep, start sawing by moving the saw up and down. A wedge inserted into the kerf prevents the saw blade from jamming.

When sawing vertically along the grain, the workpiece is fixed in the workbench with the front or rear clamp (Fig. 6). The figure shows the position of the worker's feet during the sawing process. When sawing a thin board, it is clamped so that it does not bend, lifting it up as it is sawing. Sawing begins with a gash, after which they work at full swing of the saw blade, without pressing it. Short workpieces are sawn starting from one end, and then, turning the workpiece over, from the other. Sawing of long boards (along the fibers) is carried out by resting their ends on supports (see Fig. 5).

Rice. eight. : a - correct; b - wrong (the cutting angle is too large); c - splinter cut, due to improper sawing, flakes and damage to the edges are possible; d - sawing along the fibers with a hacksaw; e - sawing with a bow saw using a template (miter box); e - sawing with a narrow hacksaw through the drilled holes; g - template for trimming the ends of boards laid in packages; 1 and 2 - side racks - saw guides; 3 - a board attached to the racks; 4 - securing the nail of the auxiliary device; detail A - position of the hand on the bow saw frame during sawing.

Sawing the workpiece across the fibers, the sawn-off end is pushed over the edge of the workbench (Fig. 7). Before starting the sawing process, the saw is done; during the sawing process, the position and inclination of the saw blade is monitored so that the kerf is straight and the surface to be sawn is even.

To avoid flaking, the cut-off part of the workpiece (Fig. 7, b) at the end of the cut should be supported by hand. For spike joints or other parts requiring mates at an angle of 45 or 90 °, use a template (miter box) (Fig. 8, e). With repeated use, the cuts on the side of the miter box may become excessively wide and will not give an exact angle. To extend the durability of the miter box, its side walls are made of hardwood boards. For trimming boards (of the same width), a special template is used (Fig. 8, jar). The side posts of the template serve as saw guides, they are made of hardwood. For boards of a certain width, an individual template is required. Sawing wood by hand is acceptable for small volumes of work.

Preparing the saw for work

Saw preparation includes planing, setting and sharpening the teeth. The shape, size and inclination of the teeth will affect how the saw operates. It is recommended to use saws with isosceles teeth only for cross-cutting, rectangular saws for longitudinal and cross-cutting, with inclined teeth - only for longitudinal sawing.

Saw planing (fig. 1) consists in aligning the tops of the teeth so that they are at the same height. To do this, a file is fixed in a vice and the tops of the teeth are moved along it. The quality of the jointing is checked by attaching a ruler to the tops; in this case, there should be no gaps between the tops of the teeth and the edges of the ruler.

Setting ... To prevent the saw blade from being clamped in the cut, the saw teeth are set apart, that is, they are bent: even - in one direction, odd - in the other. In this case, not the entire tooth is bent, but only its upper part (1/3 of the tooth apex). When spreading the teeth, it is necessary to observe the symmetry of the folds on both sides. For cutting hard rocks, the teeth are set apart by 0.25 ... 0.5 mm on the side, for soft rocks - by 0.5 ... 0.7 mm.

Rice. 2. Universal wiring: 1 - plate; 2 - adjusting screws; 3 - scale showing the amount of divorce; 4 - a screw with a stop, which regulates the height of the bent tooth; 5 - spring; 6 - lever for bending the tooth from the saw.	Rice. 3. Template for checking the correct set of saw teeth: 1 - saw; 2 - template.

When sawing raw wood, the spread should be maximum, and dry - 1.5 times the thickness of the saw blade. The kerf should not be more than twice the thickness of the blade.

It is recommended that a beginner joiner use a special wiring to open the saw (Fig. 2). The correctness of the saw set is checked with a template (Fig. 3), moving it along the blade. The saw is bred evenly, without applying great effort, as otherwise the tooth can be broken.

The teeth are sharpened with files in the shape of a rhombus or triangle, with a double or single cut. Before sharpening, the saw is securely held in a vice on a workbench. The file is pressed against the tooth when moving away from you; when returning it, lift it slightly so that it does not touch the saw. Do not press the file hard against the tooth, as this will heat up, which will lead to a decrease in the strength of the teeth.

Rip saw teeth are sharpened on one side and the file is held perpendicular to the blade. For transverse cutting, the teeth are sharpened through one and the file is held at an angle of 60 ... 70 °. Bow saws are sharpened with a triangular file.

Saws with a large tooth are bred and sharpened, and with a small one - they are mainly sharpened, but not bred. This is explained by the fact that completely dry material is used in carpentry work, the blade of bow saws is thin (0.5 ... 0.8 mm), the dimensions of the cut along the length are not particularly large, so the danger of clamping is almost excluded, and small teeth with a step of 2 ... 3 mm is very difficult to dilute. The cleanliness of sharpened but not set saws with a taut blade is much higher than that of single-handed saws with a set, which is especially important when sawing down thorns and lugs.

Working with a bow saw

To work with a bow saw, it is necessary to correctly set the blade in relation to the machine. Its angle of inclination should be 30 °; the correct rotation is adjusted with a handle. The saw blade should be straight, not skewed and well tensioned. Sawing slowly, but with confident movements; when in a hurry, the cut turns out to be uneven.

In a high-quality bow saw in working order, turning the handles should be difficult. After work, it is recommended to loosen the twist so as not to subject the stand to stress and not to stretch the blade.

When ripping, the material to be sawn must hang outward. When cross-cutting (Fig. 1, a) the workpiece lies horizontally, with longitudinal (Fig. 1, b) - it can be in horizontal and vertical positions. Usually they start sawing from the thumbnail of the left hand (Fig. 2), so this technique is called "on the nail." When sawing, the marking risk must be visible at all times. For accurate transverse cutting of the board, a miter box (shtosslad) is used, which is a box in the side walls of which there are cuts made at a certain angle (Fig. 3).

Rice. 1. Cut the boards with a bow saw: a - transverse; b - longitudinal.

Sawing along the grain with a bow saw if the material is in a horizontal position: to the right - the position of the worker's feet during sawing

For sawing wood with slanting, knots and other defects, use a bow saw with a thickened and wider (up to 50 mm) blade, circular saw, which has a narrow blade (up to 8 mm), rectangular teeth and a large set (2 - 2.5 thickness blades), as well as high machine stands, curved sawing can be performed without much effort, since a large blade spread gives a wide cut, in which the blade can be easily turned in the required direction.

When sharpening a bow saw in a vise, the file may slip and injure the hand. And it is not very convenient to hold on to the sharp edge of the file with your hand. To insure yourself against possible injury, put on the file head a tip made of a rubber tube (length - 3 ... 4 cm), cut to length on one side.

After buying a bow saw, carpenters sometimes shorten the middle, change the bowstring, make wider beam posts, since shortened machines are convenient to use, wider posts reduce their deflection when the bowstring is pulled, and with a bowstring thickness of 10 mm, an even and strong tension is obtained and it is excluded break. The bowstring is usually wrapped with a fishing line at a distance of 25 ... 30 mm from the struts at the points of abutment to the posts. In this case, in the event of a twist break, the bowstring does not fall off the machine.

For convenience, clean the handles in the bow saw with fine-grained sandpaper and cover the entire machine with oil varnish.

To tension the bow saw, it is advisable to use a lever bowstring instead of a twisting one (Fig. 4). Such a bowstring can be easily removed from two pieces of cable with a diameter of 2 ... 3 mm. The device uses a metal lever, the end of which is bent and inserted into the hole in the mullion. The degree of tension depends on the position of the hole into which the lever enters. It takes seconds to loosen or tighten the saw blade. In addition, the rope is an “eternal” bowstring. The centerpiece can be made of wood, for which it is necessary to choose a hard species (for example, beech).

To reduce the friction of the bow saw blade against the saw cut, its thickness should be reduced. To do this, fasten the canvas horizontally with a clamp to the metal base. At a distance 4 ... 1 times greater than the width of the blade, on the base, fix a metal plate 5 times thicker than the thickness of the saw (Fig. 5). Then, with a file with a large notch, resting its end on a metal plate, remove the metal layer from the saw. Do the same operation on the other side of the saw. After removing the metal, sand the blade with fine-grained emery paper.

Rice. 4. Tensioning device for bow saw: 1 - stand; 2 - cable; 3 - lever; 4 is an intermediary.

Rice. 5. Reducing the thickness of the bow saw: 1 - saw blade; 2 - metal base; 3 - a plate placed to form a thinning angle; 4 - file; 5 - clamp.

Modern bow saw is a metal tube (or rod) bent by an arc, between the ends of which the cutting blade is stretched. The rigid arc allows the cutting blade to be thin, long and narrow. Depending on the size of the arc, a blade with a large tooth (4 - 5 mm high) can be from 30 to 90 cm long. The cutting blade is attached using bolts, pins or an eccentric bracket, which makes it easy to adjust the degree of its tension.

The attachment of the cutting blade for some bow saws is carried out by means of swivel couplings. They make it possible to rotate the plane of the blade relative to the plane of the saw itself. At the beginning of the cut, the saw should be held so that the force of the hand is significantly greater than the weight of the saw. At the same time, the hand gets tired quickly, but the cut will turn out smooth.

Another simple rule of thumb is that the teeth of the bow saw should cut into the wood due to the weight of the saw itself. If you try to apply force, the thin and narrow cutting blade will start to "play", which will greatly complicate the process itself. All bow saws, the arc of which is made of a metal tube, have plastic, metal or wooden handles of different configurations and are intended only for direct hand operation.

Lumber marking

The wood is marked so that as little waste as possible is obtained from the lumber used for workpieces for parts. In other words, marking is necessary to obtain a workpiece with a minimum allowance for processing with a hand or electrified tool. For marking and checking the accuracy of processing workpieces and parts, many special and universal devices are used. For a novice carpenter, at first, mastering carpentry skills, the following tool is needed (Fig. 1):

• 5-meter tape - for linear measurements and rough marking of sawn timber;
• square - to check the angle of 90 °;
• folding rule - for any measurements in width and thickness;
• malka - for measuring and measuring angles; level - to check the horizontal and vertical location of surfaces;
• compass - for transferring dimensions to workpieces and for marking circles;
• thickness gauge - for drawing lines parallel to one of the sides of the bar or part;
• plumb line - to check the verticality of wooden structures.

Marking lines are applied with a pencil, and on a clean planed surface with an awl. On boards and other long materials, the lines are applied with a line-bend, and on light parts you should beat off with charcoal, on dark parts - with chalk.

Rice. 1. 1 - tape measure, 2 - square; 3 - folding rule; 4 - malka; 5 - level; 6 - compass; 7 - thickness gauge; 8 - plumb line; 9 - awl.

Rice. 2. a - for marking thorns; b - for marking in "dovetail"; 1 - scribe; 2 - blank; 3 - template.

Rice. 3. 1 - handle; 2 - tape measure; 3 - window for setting the required radius; 4 - body; 5 - scribe (knife); 6 - clamping bar; 7 - fastening screw; 8 - positioning needle.

It is recommended to apply the marking lines with a simple pencil of hardness T or TM. Colored pencils have a soft lead and break quickly; lines drawn with a chemical pencil will inevitably blur when the surface is wetted, resulting in contamination of the material.

The scale of divisions is often erased on a metal ruler. To avoid this, paint the cloth of the ruler treated with acetone with white or red nitro paint, and then wipe the ruler with a cloth. The paint will be removed from the ruler, and it will remain in the recesses of the numbers and marks. This will give you a clear scale of divisions. For faster and more accurate marking, it is recommended to use templates (Fig. 2), which are metal or wooden blanks of various sizes and shapes with precise dimensions applied to them. You can make such templates yourself.

There are times when it is necessary to mark out a large circle. This is usually associated with certain inconveniences. The device shown in fig. 3, simple in structure and easy to handle. Its main advantage is the ability to mark a circle of any diameter. It can be seen from the figure that the longer the metal tape of the tape measure, the larger the radius of the structure to be marked. When you replace the scriber (or pencil) with a cutter, you will receive a cutter compass.

In joinery, wooden and metal squares are used for marking. Before marking, the new wooden square is checked for accuracy by placing its outer corner against the outer corner of the metal square. The protrusions found at the wooden square are rubbed with cloth-based sandpaper. To check the inner corner, a wooden square is applied with this angle to the outer corner of the metal square, and carbon paper is placed between the contacting surfaces, which will paint the protruding irregularities of the inner corner. Then these irregularities are rubbed with a medium grit sandpaper.

Hand planing

Manual planing tool. The main tool for hand planing is the plane. All modifications of the plane (scherhebel, plane with a single and double knife, jointer) have essentially the same device (Fig. 1); They differ mainly in the thickness of the removed layer of wood and in the purity of the surface treatment of the workpiece. So, if the plane carries out rough planing (the thickness of the removed layer is 2 ... 3 mm), then the jointer completes the leveling of the surface (the thickness of the shavings is up to 1 mm).

Scherhebel conduct rough processing of wood across, along the fibers and at an angle to them (shavings are narrow and thick - up to 3 mm). A plane with a single knife is used to level the surface after sawing and using a scherhebel. More convenient in terms of surface frequency is a double-knife planer with a chipbreaker, which eliminates surface defects - scoring and chips. In addition to wooden tools, metal scherhebelles and planes with single and double knives are used mainly for repair work in an apartment. The jointer performs surface finishing. It has a long block, which, when planing long parts, has a positive effect on the quality of the processed surface. Planed with a jointer until clean and even shavings go.

A tool with a wooden block is used for basic work, and with a metal sole and body - in cases where the wooden surface of the tool can be damaged (planing of hard ends, chipboard and non-wood materials - plastic, plexiglass, ebonite, hardboard, etc.). In the process of work, a wooden tool gives less stress on the hands, which means less fatigue. In addition, the friction of such a tool is low, its sliding on the surface is better than that of a metal one.

In carpentry, it is sometimes necessary to plan small and narrow parts. Ordinary carpentry tools are too big for this, but small planers are suitable for such work.

In addition to tools that make it possible to process products with planar planing, special tools are also used for shaped processing of grooves and edges (Fig. 2).

The sampler is used for picking out quarters in rectangular parts and for processing edges. The falzgebel is similar to a sampler, but its sole has a stepped structure. It serves to select quarters, which are then cleaned with a zenzub.

The zenzubel is used to select longitudinal grooves in the form of right angles (folds) on the edges of parts. The blade of such a zenzub is straight and forms a right angle with the lateral edge of the gland. A chisel with a slanting piece of iron is used to clean the folds cut with another tool. Such a zenzub should not be confused with the helical zenzub, which is used to process dovetail profiles.

The groove is used to select narrow grooves (grooves) and quarters in a rectangular part, and the groove is used to select ridges and grooves on the edges of parts.

With a staple, they arrange roundings on the edges of the parts; its block and knife have a concave rounded surface. Kalevka perform figured processing of the front edges of the parts. The fillet is used to select grooves in the details. Concave and convex surfaces are treated with humpback.

When buying wooden blocks, pay attention to the sufficient allowance on the shoulders, to which the wedge is pressed from below, and at a distance from the edge of the slot to the end of the knife (when assembled, it should not exceed 2 mm). Typically, after purchase, wood pads are kept at room temperature for about three months. In addition, the wooden blocks are adjusted "under the arm", removing seizures, dulling the ribs, sanding the walls and covering the sides and top with oil varnish. The hole of any tool should not have chips or scuffs.

Tool setting. The set-up work includes disassembly and assembly of the tool, as well as replacement and fastening of the knife. To disassemble the plane, it is enough to hit the tail end with a hammer, and to assemble, you need to lay the knife and hit the front end. Consequently, the overhang of the knife will increase when hitting the front end and decrease when hitting the tail end. The knife is set at a certain angle to the horizontal plane. For basic planing operations with the scherhebel, single and double knife planers, zenzubel, this angle is 45 °, zinubel - 80 °. The jointer knife is taken out by striking its cork.

The blade of the iron of the planer should protrude from the plane of the sole to the thickness of the removed shavings. First, the blade of the piece of iron is installed, then its angles are adjusted. When positioned correctly, the chips should be the same width in all areas. The piece of iron is fixed like this: the shoe is placed with the sole on the flat surface of the board and, pressing the board with the left hand, insert the piece of iron into place with the right hand. The piece of iron is exposed so that it protrudes from the plane of the sole to the required length: for a planer with a single knife - up to 1 mm, for a scherhebel - up to 3 mm, etc. For metal planers, the knife is adjusted using a screw. After each adjustment, it is necessary to carry out a trial planing.

For double knives, the second knife, which is also called a chipbreaker, is set with a minimum gap with respect to the first knife. When adjusting planers, it is often necessary to sharpen the blade. Its cutting edge is sharpened at right angles to the side rib.

Manual planing. Before proceeding with planing work, it is necessary to select wood, that is, to establish its suitability for the manufacture of any part. At the same time, convexities and concavities to be removed by planing, as well as wood defects, are identified and it is determined whether they are permissible for this part. For planing, the workpiece must be secured so that the direction of the wood grain coincides with the direction of planing. The deflection of the workpiece indicates that the fastening should be slightly loosened. At the beginning of planing, the tool is pressed with the left hand, the efforts of both hands are leveled towards the middle, and at the end they are pressed with the right hand so as not to jam the end of the part. They plan calmly, slowly, but confidently, in full swing, with a uniform feed of the tool in all areas. The body of the worker should be slightly tilted forward, the left leg extended forward, and the right one should be at an angle of 70 ° in relation to the left. The quality of planing is controlled with a ruler, well-calibrated bars and a square. If there are no gaps between the ruler and the planed workpiece, the tool is finished.

When planing, the surface cleanliness depends on the distance from the chip cleavage to the knife blade (the closer the chip is from the tap hole, the cleaner the planing), as well as on the steepness of the chip crease when entering the tap hole (a steep crease is cut faster with a knife, resulting in a shorter length chip). In a double-knife planer, the function of breaking the chips is performed by the second knife, and the closer it is to the blade of the first knife, the cleaner the surface is. Usually the width of the chipbreaker (second knife) does not exceed the width of the first knife. The state of the gap and the cutting part of the knives can be recognized by the appearance of the chips coming out of the taphole. If the chipbreaker is blunt, the chips come out straight and the planing surface is clean, if it is very sharp, the chips come out in rings, so the sharpened edge of the chipbreaker is slightly blunt.

In carpentry, drilling is used to make holes for round spikes, screws and other metal elements when joining parts, for plugs when removing knots, for grooves when processing wood with a chisel and chisel. The principle of operation of any drill is that it, going deeper into the wood, selects the material with its cutting edges, forming a hole.

Drill types and preparation for work

Drills are feather, center, spiral, screw (Fig. 1). A drill is distinguished by a shank, a rod itself, a cutting part and elements for removing chips.

Feather drills type of spoon perk have the form of an elongated trough with sharp edges (see Fig. 1, a). They serve for drilling holes for pins with a diameter of 3 ... 16 mm (with a drill length up to 170 mm). During the drilling process, the perk is periodically removed from the wood to remove chips. The disadvantage of the pen drill is the lack of a guiding center. For drilling holes of larger diameter, use perforated drills of other designs (see Fig. 1, b).

Center drills(see Fig. 1, c) drilled through, but shallow holes across the grain of the wood, since the exit of the shavings in them is difficult. Such drills work only in one direction and when pressed from above. Their diameter is up to 50, length is up to 150 mm.

Twist drills(see Fig. 1, d) are more perfect in their design. They provide for the removal of chips, as a result of which the hole is not clogged when drilling with chips and has clean, even walls. As well as centering, these drills have a center and an overcutter or a tapered cutting edge. The diameter of drills with conical sharpening is 2 ... 6 mm (short series) and 5 ... 10 mm (long series), and with center and cutter - 4 ... 32 mm. Conical ground drills are used for drilling along the grain, with a center and a scorer - across. Twist drills can be fitted with tungsten carbide inserts for extra hard woods.

Twist drills(see Fig. 1, e) is used mainly for drilling deep holes across the grain of the wood. After passing this drill, the walls of the hole are clean. Drill diameter t - up to 50, length - up to 1100 mm.

For drilling holes of large diameters, use cork drills, and to expand the holes for the heads of screws or nuts - countersinks (Fig. 2). When drilling wood, drills for metal are also used, reducing their sharpening angle.

The drill must be properly sharpened, otherwise it will tear, not cut the wood, and the hole will be clogged with shavings. When sharpening, the cutting edges must be kept straight. Since the cutting head has a limited supply of metal, the drill must be sharpened carefully and economically. It is sharpened on an abrasive stone (Fig. 4, a) or manually with a thin square file, and adjusted with a special touchstone. Typically, the drill angle is 12 °.

Center drills start sharpening from the inside of the cutting edge, the rest from the outside. The correctness of sharpening is checked with a template (Fig. 4, b). The ends of the lateral cutters must protrude at least 3 mm above the cutting edges of the horizontal cutters. This allows the tabs to start cutting before the horizontal cutters begin to cut the chips.

The way the drill is sharpened determines, first of all, the cleanliness of the hole processing and the drilling accuracy. The transverse cutting edge must pass through the axis of the drill. When it is displaced from the axis, the drill will move to the side, as a result of which uneven wear of the cutting edges and beating of the drill will occur, and, consequently, an increase in the diameter of the hole.

Rice. 1. Drills for working with wood: a, b - feather; in - center; d - spiral; d - screw.	Rice. 2. Cork drill (a) and countersink (b).
Rice. 3. Device for drilling large-diameter holes: 1 - drill chuck; 2 - metal rods; 3 - wooden circle; 4 - saw blade; 5 - centering drill.	Rice. 4. Sharpening the drill on the sharpener (a) and checking the correctness of sharpening according to the template (b).
Rice. 5. Manual screw drill (a) and brace (b): 1 - push head; 2 - handle; 3 - threaded steel rod; 4 - clamping chuck; 5 - ring, switch; 6 - ratchet mechanism.	Rice. 6. Additional tool for drilling: a - drill; b - gimbal; c - spoon drill.

To drill a large number of identical holes in an array, you must have several drills of the same diameter in stock. Replacing the drills periodically will increase their service life.

Manual drilling in wood. The wood is drilled with a drill and brace. To fix the drills in them, clamping chucks of various designs are used.

Hand Helical Drill(Fig. 5, a) serves mainly for drilling holes with a diameter of up to 5 mm. Its shaft has a screw thread for moving the handle. The force from the hand gripping the handle is transferred to the rod, and the ok starts to rotate. The second hand acts on the pressure head. From the combination of these two efforts, the drill is introduced into the wood, that is, the cutting process.

Have brace(Fig. 5, b) the cutting process comes from the effort that the worker's hand creates when the crank arm rotates with the handle in the middle. At the bottom of the rod there is a ratchet chuck, which makes it possible to set the rotation to the right and left. Drills with a diameter of up to 10 mm can be fastened to the rotor.

To drill holes, their centers must be marked. When marking, take into account the hardness of the wood, the degree of its splitting awn, the location of cracks and knots, the direction and depth of drilling, the presence of nails, metal staples, etc. Usually, the centers of the holes are pierced with a scriber or a triangular awl to the depth of the drill diameter. When drilling holes of large diameters, their centers are pre-drilled with thin drills so that the drill does not go to the side. The centers of deep through holes are drilled on both sides; in this case, the drilling process itself is performed in the same way (i.e., from both sides). The diameter of the drill for drilling for screws should be 0.5 mm less than the diameter of the middle part of the screw. In brittle wood and at the ends for the screw heads, it is recommended to lower (countersink) so that during further operations (priming, filling and painting) the screw heads are flush with the surface of the part.

When making through holes, it is necessary to put an obstacle at the exit of the drill (for this you can use a piece of wood), otherwise chips or cracks will inevitably form in the workpiece. When drilling, the tool must not be turned towards you. It is not recommended to work with unsharpened drills and drills with chips of the cutting part and cracks. You should pay attention to the centering of the drill in the chuck, since the correct drilling depends on this. The drill will inevitably go to the side from strong beating. Sharpening the drill correctly will avoid excessive force and a torn surface. An increase in the applied force leads to damage to the part and breakage of the drill, and also creates a traumatic situation.

To drill deep holes in solid wood, use drill(Fig. 6, a), and shallow holes in hardwood for screws - gimlet(Fig. 6, b). The drill is a metal rod with an eyelet for the handle at the top and a screw surface with a guiding center at the bottom. The drill has difficulty in removing the chips from the hole, so it is periodically removed from the hole and cleaned of chips. The drill and gimbal do not give the cleanliness of processing that can be obtained when drilling with drills. Carpentry craftsmen have spoon gimbals (Fig. 6, c). In fact, these are the same perks, only with a sharp tip and a taper screw.

The method of working with a drill is as follows: first, it is installed in the intended place with a tip, and then with a certain effort it is pressed against the tree. When the tip goes deep into the wood, no further pressure is needed, you just need to turn the tool by the handles. Unfortunately, the drill does not cut, but tears the wood, and sometimes cracks and splits appear in the workpiece, especially near the end. Drills are used for irresponsible joinery and carpentry.

Splicing and joining wood

Splice It is widely used to obtain long beams, in the construction of furniture frames, connecting skirting boards, making drawers for table covers, etc. The most widespread is a serrated connection (as the most durable), which forms a large bonding area. One and a half parts of the parts are spliced ​​at the skirting boards when tying the panels, that is, for parts that do not experience significant stress. Trimming is carried out in a marking box (miter box) at an angle of 45 °. A sharper angle is used with an increased load, especially for bending.

Parts under tensile stress are spliced ​​with an open dovetail spike. Parts with a support at the bottom, which are experiencing forces tending to displace them in different directions, are spliced ​​onto a plug-in round tenon. When replacing parts in a product, they are used to grind them, which is performed by splicing or growing, depending on the shape of the part in section (Fig. 2).

Rice. 1. : a - end; b - on the "mustache"; c - toothed.

Rice. 2. : a - half a tree; b - an oblique cut; in - in a straight patch lock; d - in an oblique patch lock, d - in a straight tension lock; e - in an oblique tension lock; w - end-to-end; h - end-to-end with a secret spike; and - end-to-end with the end ridge; k - end-to-end with a plug-in thorn (pin); l - in half a tree with bolt fastening; m - half a tree with strip iron fastening; n - in half a tree with fastening with clamps; o - with an oblique cut and fastening with clamps; n - end-to-end with overlays.

Rice. 3. Joining wood by means of rallying along the width of the edge: a - on a smooth joint; b - a quarter; c - into a rectangular groove and a ridge along the edge; d - in a trapezoidal groove and a ridge along the edge; d - in the groove and rail.

Rallying used in cases where it is necessary to join the joinery material along the width of the edge into shields or blocks (Fig. 3). The most common method of rallying is smooth fugue rallying. In this case, the edges of the abutting sections are pressed tightly along the entire length and compressed with glue. In addition to this simple method, jointing on a jointer and insertable round or flat tenons are also used. The rallying in a quarter is carried out dry, without glue, and the sponge of the quarter extending to the non-front side should be 0.5 mm narrower than the sponge extending to the front side. Joining into a groove and a ridge is performed with and without glue. Fusing into a groove on a rail with precise jointing of the abutting areas and high-quality gluing is the most durable and economical, since the material for the ridge is taken from wood waste.

Bending technology for joinery

When making furniture, you cannot do without curved details. You can get them in two ways - by sawing and bending. Technologically, it would seem, it is easier to cut a curved part than to steam it, bend it and then hold it until it is ready for a certain period of time. But sawing has a number of negative consequences.

First, there is a high probability of cutting the fibers when working with a circular saw (it is she who is used with this technology). The consequence of cutting the fibers will be the loss of strength of the part, and, as a consequence, the entire product as a whole. Second, the cutting technology involves a higher consumption of material than the bending technology. This is obvious and no comment is required. Third, all curved surfaces of the sawn-off parts have end and one-and-a-half cut surfaces. This significantly affects the conditions for their further processing and finishing.

Bending avoids all of these disadvantages. Of course, bending presupposes the presence of special equipment and devices, and this is not always possible. However, bending is also possible in the home workshop. So what is the technology of the bending process?

The technological process of manufacturing bent parts includes hydrothermal treatment, bending of workpieces and their drying after bending.

Hydrothermal treatment improves the plastic properties of wood. Plasticity is understood as the properties of a material to change its shape without destruction under the influence of external forces and to maintain it after the action of the forces is eliminated. Wood acquires the best plastic properties at a moisture content of 25 - 30% and a temperature in the center of the workpiece by the time of bending about 100 ° C.

The hydrothermal treatment of wood is carried out by steaming in boilers with saturated low pressure steam of 0.02 - 0.05 MPa at a temperature of 102 - 105 ° C.

Since the duration of steaming is determined by the time it takes to reach the set temperature in the center of the preform to be steamed, the steaming time increases with increasing thickness of the preform. For example, for steaming a workpiece (with an initial moisture content of 30% and an initial temperature of 25 ° C) 25 mm thick with a temperature in the center of the workpiece reaching 100 ° C, 1 hour is required, 35 mm thick - 1 hour 50 minutes.

When bending, the workpiece is placed on a tire with stops (Fig. 1), then in a mechanical or hydraulic press the workpiece together with the tire is bent to a predetermined contour; in presses, as a rule, several workpieces are bent simultaneously. At the end of bending, the ends of the tires are pulled together with a tie. Bent workpieces go to drying together with tires.

The workpieces are dried for 6 - 8 hours. The form of the workpieces is stabilized during drying. After drying, the blanks are freed from templates and tires and kept for at least 24 hours. After holding, the deviation of the dimensions of the bent blanks from the initial ones is usually ± 3 mm. Next, the workpieces are processed.

For bent blanks, peeled veneer, urea-formaldehyde resins KF-BZh, KF-Zh, KF-MG, M-70, chipboards P-1 and P-2 are used. The thickness of the workpiece can be from 4 to 30 mm. Blanks can have a wide variety of profiles: corner, arcuate, spherical, U-shaped, trapezoidal and trough-shaped (see Fig. 2). Such blanks are obtained by simultaneously bending and gluing together veneer sheets greased with glue, which are formed into packages (Fig. 3). This technology makes it possible to obtain products of a wide variety of architectural forms. In addition, the manufacture of bent-glued veneer parts is economically feasible due to the low consumption of timber and relatively low labor costs.

Layers of plots are smeared with glue, laid in a template and pressed (Fig. 4). After holding under the press until the glue sets completely, the knot retains its shape. Bent-glued units are made from veneer, from hardwood and coniferous plates, from plywood. In curved veneer elements, the direction of the fibers in the veneer layers can be either mutually perpendicular or the same. The bending of veneer, in which the grain of the wood remains rectilinear, is called a bend across the grain, and in which the fibers bend is called a bend along the grain.

When designing bent-glued veneer units that carry significant loads during operation (legs of chairs, cabinet products), the most rational structures are those with bending along the fibers in all layers. The rigidity of such knots is much higher than that of knots with mutually perpendicular wood grain direction. With the mutually perpendicular direction of the veneer fibers in the layers, bent-glued units up to 10 mm thick are designed that do not bear heavy loads during operation (box walls, etc.). In this case, they are less subject to shape change. The outer layer of such nodes should have a lobe direction of the fibers (bending along the fibers), since when bending across the fibers, small lobe cracks appear at the bending points, which exclude a good finish of the product.

Allowable (radii of curvature of bent-glued veneer elements depend on the following design parameters: veneer thickness, number of veneer layers in a package, package design, billet bending angle, mold design.

When manufacturing bent sections with longitudinal cuts, it is necessary to take into account the dependence of the thickness of the bent elements on the type of wood and the thickness of the bent part.

In the tables, the elements remaining after the cuts are called extreme, the rest are intermediate. The minimum distance between cuts that can be obtained is about 1.5 mm.

With an increase in the bending radius of the slab, the distance between the cuts decreases (Fig. 5). The kerf depends on the bending radius of the slab and the number of cuts. To obtain rounded nodes, a groove is selected in the slab after veneering and grinding in the place where the bend will be. The groove can be rectangular or dovetail. The thickness of the remaining plywood lintel (the bottom of the groove) should be equal to the thickness of the facing plywood with an allowance of 1-1.5 mm. A rounded bar is inserted into the rectangular groove on the glue, and a strip of veneer is inserted into the dovetail groove. Then the board is bent and held in a template until the glue sets. To give the corner more strength, you can put a wooden square in it from the inside.

Spike connections

The simplest joinery connection can be thought of as connecting a tenon into a socket or an eyelet (Fig. 1). A thorn is a protrusion at the end of a bar (Fig. 2), a socket is a hole into which a thorn enters. Spike joints are divided into corner end, corner center and corner box.

In the practice of amateur carpenters, corner end connections are very common. To calculate the elements of such connections, Fig. 3 and table.

Suppose it is necessary to calculate a mustache connection with a plug-in through flat tenon (UK-11). The thickness of the bar to be connected is known (let s0 = 25 mm). Then, taking this size as a basis, we determine the size s1. According to the table, s1 = 0.4 mm, s0 = 10 mm.

Let's take the UK-8 connection. Let the diameter of the pin be 6 mm, then l (we choose the average value - 4d) is 24 mm, and l1 = 27 mm. Connections with pins are made symmetrically to each other and in relation to the plane of the part, therefore, according to Fig. 3 h, the distance from the center of the hole for the lower dowel to the center of the hole for the upper dowel will be at least 2d, or 12 mm; the same distance from the center of the hole of the dowel to the end of the connected part.

In fig. 4 shows diagrams of corner mid (tee) connections , for which, when calculating, it is necessary to observe the following basic dimensions of spikes and other elements: in the US-1 and US-2 joints, the use of a double spike is allowed, while s1 = 0.2s0, l1 = (0.3 ... 0.8) B, l2 = (0.2 ... 0.3) B1; in the compound US-3 s1 = 0.4s0, s2 = 0.5 (s0 - s1); in the compound US-4 s1 = s3 = 0.2s0, s2 = 0.5 X [s0 - (2s1 + s3)]; in the joint US-5 s1 = (0.4 ... 0.5) s0, l = (0.3 ... 0.8) s0, s2 = 0.5 (s0-s1), b ≥ 2 mm; in the joint US-6 l = (0.3 ... 0.5) s0, b ≥ 1 mm; in the joint US-7 d = 0.4 at l1> l by 2 ... 3 mm; in the compound US-8 l = (0.3 ... 0.5) B1, s1 = 0.85s0.

Dimensions of cleats and other corner end fittings

Connections	s 1	s 2	s 3	l	l 1	h	b	d
UK-1	0.4s 0	0.5 (s 0 - s 1)	-	-	-	-	-	-
UK-2	0.2s 0	0,5	0.2s 0	-	-	-	-	-
UK-3	0.1s 0	0,5	0.14s 0	-	-	-	-	-
UK-4	0.4s 0	0.5 (s 0 - s 1)	-	(0.5 ... 0.8) V	(0.6 ... 0.3) l	0.7B 1	≥ 2 mm	-
UK-5	0.4s 0	0.5 (s 0 - s 1)	-	0.5V	-	0.6B 1	-	-
UK-6	0.4s 0	0.5 (s 0 - s 1)	-	(0.5 ... 0.8) B	-	0.7B 1	≥ 2 mm	-
UK-7	-	0.5 (s 0 - s 1)	-	-	-	0.6B 1	-	-
UK-8	-	-	-	(2.5 ... 6) d	l 1> l by 2 ... 3 mm	-	-	-
UK-9	-	-	-	(2.5 ... 6) d	l 1> l by 2 ... 3 mm	-	-	-
UK-10	0.4s 0	-	-	(1 ... 1,2) B	-	-	0.75B	-
UK-11	0.4s 0	-	-	-	-	-	-	-

Note. The sizes s0, B and B1 are known in each case.

Rice. 1. : a - into the nest; b - in the eyelet; 1 - thorn; 2 - socket, eyelet.

In corner box joints, the spikes are repeated many times. Basically, three types of such connections are used: on a straight open thorn (see Fig. 3, a); an open “dovetail” thorn (see Fig. 2, e); on an open round plug-in thorn - a dowel (see Fig. 3, h).

The dowel (dowel) connection method is often used. A dowel is a cylindrical stick made of birch, oak, etc. It is smoothly turned and hammered into pre-drilled holes - channels pre-greased with glue. Holes for dowels are made in both parts at once. The dowel should fit into the hole tightly, with the help of blows from a mallet. The drill for preparing the holes must match the dowel dimensions. To reduce the diameter of the dowel, sanding with emery paper or a fist file is used (the risks are made not across, but along the dowel).

When choosing a connection, it is necessary to take into account, first of all, the nature and magnitude of the load, as well as how the connection will resist the load. For example, when connecting a cabinet shelf end-to-end with a wall, the entire load will fall on the screws or dowels. The force with which the product (shelf) presses on them makes them resist crosscut and break. Therefore, the load is made here small. In this case, it is more expedient to install a wooden rail under the shelf, screwing it tightly to the cabinet wall. The load will increase, but the resistance to it will also increase due to not only screws, but also friction between the rail and the cabinet wall. A significantly greater load can be tolerated if the shelf is cut at least to a small depth into the wall mass; in this case, the load will be perceived by the furniture wall itself.

Rice. 3. : a - on a single open end-to-end thorn - UK-1; b - on an open through double thorn - UK-2; c - on a thorn open end-to-end triple - UK-3; d - on a thorn with a semi-dark blind - UK-4; d - on a thorn with a semi-dark through UK-5; e - on a blind thorn - UK-6; g - on a thorn with darkness through - UK-7; h - on round plug-in, blind and through thorns - UK-8; and - on the "mustache" with a plug-in blind round thorn - UK-9; k - on the "mustache" with a plug-in blind flat thorn - UK-10; l - on the "mustache" with a plug-in through flat tenon - UK-11.

Rice. 4. : a - on a single blind thorn - US-1; b - for a single blind sewn into a groove - US-2; c - on a single through thorn - US-3; g - on a double through thorn - US-4; d - into the groove and the blind ridge - US-5; c - into the blind groove - US-6; g - on round plug-in blind pins - US-7; h - blind “dovetail” thorn - US-8.

Comparison of the resistances of the two joints (half-tree with a screw and one in "dovetail") shows that the joint in "dovetail" withstands a load three times greater than the joint in half-tree with a screw. Based on this and a number of other examples, the following conclusions can be drawn about the advisability of using certain joints: joinery knitting should be selected in accordance with the magnitude and direction of the load on the joint; the load should be perceived directly by the design of the product itself (additional fasteners can be a screw, metal square, dowel, etc.); knitting with gaps is not allowed.

Bonding should be done only with prepared surfaces: the rougher, for example, the surface of the dowel, the more reliably it will stick to the solid.