The knife blades of various lawn mowers are almost always made of high quality steel, however, despite this, they still need to be sharpened periodically. And the main thing is to do it so as not to degrade the quality of the metal. However, no special tools and skills are not required for this, and any summer resident will easily be able to cope with such a task!
Why do lawn mower knives need to be sharpened?
Of course, it is quite possible to cut off the excess of juicy green grass from your favorite lawn with a knife with blunt edges. But the grass, as a result of such manipulations, will begin to delaminate (this stratification will go mainly in the longitudinal direction), gradually turning into a sloppy fringe. And after a few days, it will dry out altogether and may even get sick for several weeks. That is why the cuts should always be neat and even - in this case, they take only a few hours to tighten and allow you to maintain a spectacular juicy green color of the lawn. And in order for them to be such, you need to periodically sharpen the knives of the lawn mowers used!Remove the knife
Before embarking on such an important event, it is important to try to protect yourself and your garden gadget as much as possible. This is especially true for gasoline lawn mowers (models with an electric drive are easily neutralized by an elementary disconnection from the network): first you need to free the spark plug from the cap, and then you need to completely eliminate the possibility of fuel leakage. This can be done in two ways - both by draining the tank and by placing a rubber sealed membrane under the lid and shutting off the fuel cock. Unless instructed otherwise, turn the mower towards the handle only. And before doing this, you should pinch the hose intended for the exhaust of crankcase gases - this will help to avoid oil leakage.
Knives in different models lawnmowers come in a wide variety of configurations, but the bolt threads always loosen the same counterclockwise. And to prevent possible rotation of the shaft, you can place a block firmly rested in the ground under the knife. And, of course, in order not to confuse anything when setting the knife back, it is important to try to remember or even sketch the position of the blades.
What to do next?
The removed knife must be cleaned of hardened herbal juices, as well as dirt adhering to it. The easiest way to do this is using a metal brush. The surface of the knife is then examined for any curvatures or bumps. If there are any, they are straightened with an ordinary hammer with slightly rounded edges of the striker. As a rule, the knife begins to straighten from the edges of the curved section, gradually moving towards its center. It also does not hurt to check the kickback blades, which are often unbending from impacts, because if they bend at unequal angles, this will inevitably lead to a deterioration in the air flow, as a result of which the cut grass will simply not be mulched properly.The next step is pulling out the descent. First, they get rid of chipped chips, bringing out the edge of the blade at the same angle along the entire length of the cutting part. A small file or an electric sharpener equipped with a carborundum stone will help to bring the descent to the required angle. In this case, it is important to try to remove the metal from the knife as evenly as possible. But the grinder for these purposes is categorically not recommended, since it can significantly degrade the quality of the sharpened blade.
Sharpening the blade
For sharpening the blade, a flat emery bar is usually used, the grit of which ranges from 400 to 600 grit. Before you start sharpening the blade, it is recommended to soak the bar for ten to fifteen minutes in soapy water. Periodically, during the sharpening process, this manipulation must be repeated. And the knife should be sharpened by pulling the bar in the direction from the center of the sharpened area to its edge. In this case, it is desirable that the stone is in the same position - this will contribute to maintaining a constant angle. And, of course, the same amount of metal should ideally be grinded from the blades of the knife!
Sharpened blades also need to be "corrected" - for this you need a small piece of moisture-resistant sandpaper, the grain size of which has a range from 600 to 800 grit. The paper is moistened with water and rolled into a cylinder, the diameter of which reaches about 100 - 150 millimeters, and only after that the "straightening" is started. And before installing the blade back on the mower, it is important to make sure that the weight of its shoulders remains the same, otherwise (in case of imbalance) extremely unwanted vibration may occur. To check the balancing, first a smooth rod is clamped horizontally in a vice, and then a blade is put on it through the hole in the middle and they also try to set it horizontally, observing its behavior - one shoulder should not noticeably overtighten the other. If the balance is not observed, then a little more metal is grinded from one of the shoulders. And only then can the sharpened blade be put back on the mower!
Despite the fact that the blades of the lawn mower are made of high quality steel, from time to time they have to be refreshed. Fortunately, this does not require special skills and equipment, and today we will tell you how to sharpen a lawn mower knife yourself without deteriorating the quality of the metal.
It is possible to cut off excess grass from the lawn even if the edges of the mower blade are obviously dull. However, in this case, the shoots will delaminate in the longitudinal direction, turning into a fringe. A few days after mowing, the grass will become dry and sore for several weeks. The cut should be even and neat, then it will take just a few hours and the lawn will always be juicy green. This requires the knife to be almost perfectly sharpened.
Left: grass cut with a blunt lawn mower blade. Right: grass cut with a sharp blade
How to remove a knife from a lawn mower
Before proceeding with the partial disassembly of the lawn mower, you need to protect yourself and her. While an electrically powered device can be easily disconnected from the mains, petrol lawn mowers require preliminary preparation. The first step is to remove the spark plug cap. Next, you should exclude fuel leaks, that is, either drain the tank, or put a sealed rubber membrane under the lid and turn off the fuel cock. Turn the mower only towards the side of the handle, unless otherwise explicitly stated in the operating instructions. Before turning the mower over, be sure to pinch the crankcase exhaust hose to avoid spilling oil.
Lawn mowers use different blade configurations. In the simplest case, this is an ordinary two-bladed plate. complex shape, however, the knife can also be composite - the upper blade is designed for mulching the cut grass. There are also four-bladed knives, which can be both composite and on a common base.
The knife can be attached either with one bolt in the center through a shaped washer, or with two bolts with a fit on a centering hole or pin. In any case, the thread on the bolts is right-hand, respectively, it is necessary to unscrew it counterclockwise. To block the shaft from rotating, place a block under the knife, resting on the ground. It is advisable to remember or outline the position of the blade (s), so as not to confuse anything when reassembling. Temporarily screw the unscrewed bolts into the free holes.
Cleaning and straightening
When the knife is removed, it must first be cleaned of adhering dirt and hardened herbal juice. The easiest way to do this is with a metal brush. The knife strip must be clean on all sides: not until metallic luster, but without the smallest adhering fragments.
Often due to falling into working area hard objects such as stones and chips, the blade deforms quite noticeably. Most blades are not straight by themselves, but the cutting edge and strip 10-15 cm away from it should be examined for local bumps and curvatures. This is done using a short, straight ruler.
You can straighten the blade with an ordinary hammer, with the edges of the striker slightly rounded. The knife is laid on a flat massive support (anvil), then the correct shape is given to the metal with weak blows. You need to edit the knife, starting from the edges of the curved section, gradually moving towards the center. A curved blade body is a minor problem, but it is very important that the cutting parts are straightened in a straight line. You also need to check the kickback blades, which often straighten from impact. If the blades on different knife arms are bent at different angles, this will impair the air flow and the cut grass will not mulch properly.
Taking out descents
If the knife long time did not sharpen, chipped chips are likely to appear on it. You need to get rid of them by bringing out the edge of the blade at a uniform angle along the entire length of the cutting section. Please note that there may be several edges on each side, in which case the mower will have multiple cutting edges.
Lawn mower blades are sharpened on one side, the slope of which, as a rule, is directed upwards. To bring the descent at the desired angle, you should use an electric sharpener with a carborundum stone, and in the absence of one, a fine file. It is very important to remove metal evenly from both blades. Therefore, keep the same pressure and at least roughly count the number of passes of the sharpener.
Small deviations of the sharpening angle are not critical, however, the smoother the slopes are brought out, the longer the knife resource will be. When shaping the blade, it always moves onto the grain to avoid the formation of large burrs and flakes. You should not use a grinder for preliminary sharpening - overheating can deteriorate the quality of the metal. However, you can install a flap or disc disc under sandpaper on the angle grinder.
Sharpening the blades
The purpose of sharpening itself is to eliminate small edge chips and bring the descent into one straight plane. The presence of a "file" on the blade leads to a rapid decrease in sharpness, and with a rounded descent, too much effect on the cut stems is exerted. In addition, the rounded blade gets dirty much faster.
Sharpening the blade is best done with a flat emery bar with a grain size of about 400-600 grit, there is no particular point in using more "delicate" stones. Soak the block in lathered water for 10-15 minutes and wet it periodically while turning. The knife is also sharpened on the grain with a small broach of the bar from the center of the sharpened area to the edge.
When sharpening, try to keep the same position of the stone to maintain a constant angle. As with pulling out slopes, sharpening should be carried out with the condition that the same amount of metal is removed on opposite blades. This condition, however, does not have to be strictly observed when sharpening four-bladed knives.
Editing edges
When the blades are sharpened, they need to be straightened. This is done using a piece of moisture-resistant sandpaper with a grain size of about 600-800 grit. The paper must be moistened with water and rolled into a cylinder with a diameter of 100-150 mm.
Editing aims to remove the slightest burrs and flakes that can wrap around the thinnest edge of the blade. The sandpaper rolled into a cylinder should be lightly pressed against the descent plane and pulled smooth movement from grain. In this case, it is also recommended to make a smooth offset from the center to the edges.
When removing the triggers and sharpening, all manipulations were carried out with only one side of the blade. During the dressing process, the knife is also processed from the back side. Here the paper is pressed almost close to the body of the knife, but with a slight tilt towards the edge. The paper clamping force when editing is very small, but a lot of movements need to be made, trying to eliminate large scratches on the brilliant escapement, which remained after sharpening.
For reference: You can also sharpen a lawn mower knife with a rivet, by analogy with a conventional manual scythe. This, however, requires a special adaptation - grandmother, as well as a specific skill. But on the other hand, with this method of sharpening, you will not need to balance the knife.
Balancing check
Before attaching the blade back, you need to make sure that its shoulders are at least about the same weight. Otherwise, vibration will occur during operation, which will not have a positive effect on the durability of the spindle.
Balancing is carried out mainly for double-sided single and compound knives, four-bladed ones are not so strongly subject to imbalance. To check the knife, you need to clamp a smooth bar in a vice in a horizontal position. The blade is put on it through the hole in the center, after which attempts are made to install it strictly horizontally. If one of the shoulders weighs significantly more than the other, the knife will steadily turn to one side.
The shoulder weight equation is carried out by grinding a small amount of metal from the back of one of the knife arms. It is not necessary to achieve ultra-precise balancing, however, the knife should be held in a strictly horizontal position for at least a few seconds. When balancing is done, you can put the knife back in place and finally refresh the look of your lawn.
A sloppy lawn immediately after mowing is a sure sign that lawn mowers the knife is dull. There can be two solutions: sharpen the knife yourself or take it to the service. Let's start with the first option.
How to sharpen a lawn mower knife yourself
For convenience knife better to remove (read more in our instructions). Be sure to drain the fuel tank and oil from the crankcase before turning the mower over. Alternative way- put the mower on a solid frame or at least two stools to "crawl" from below.
Sharpening by hand
If the knife is not too dull, it is enough to correct the edges with a flat file.
- First, remove any rust (if any) with a wire wool or a brush.
- Don't be as sharp as a razor - remove rounds and burrs.
- Try to keep the original sharpening angle and sharpen both blades evenly. Otherwise, an imbalance will appear, and the blade will "walk" from side to side. As a result - quick wear of bearings and replacement of the engine.
To check the balance, you need to hang the knife by passing a pencil or nail through the center hole. Next, we see if one of the parties outweighs. If so, then on the heavier side, you still need to go through the file.
Sharpening on the machine
ATTACH_BLOCK ">Where to sharpen a lawn mower knife
If you do not have the skills or suitable equipment, it is more correct to contact service center... Ask the craftsmen to check the balance of the knife. Then he is guaranteed to serve for more than one season. The new blades should also be taken to the workshop - they also have an imbalance.
And finally, a couple of tips:
- Wear gloves - it costs nothing to cut yourself with a knife.
- Use a vise to clamp the knife.
- Check the condition of the knife at least once a month during the season.
The lawn mower blade has 2 cutting edges. In this case, the metal plate is monolithic, and not divided into 2 parts, since it is driven from one rotor. And it is with this that the biggest difficulty is connected - the correct balancing of the knife. If one of the parts is broken more than the other, an imbalance will occur. The blade during operation will vibrate and rapidly wear out the rotor drive. What tools can you sharpen knives with? Could it be that you have to work with stone?
Necessary tools for sharpening
The first thing to pay attention to is how the knife is removed correctly. Lawn mower with gasoline engine in no case should it be turned upwards with a disc and a protective casing, as oil and fumes remaining in the cylinders will get into the carburetor area.
You need to turn the mower to the side, and in the direction of the control knobs. If possible, it is advisable not to do this either, but to use the flyover. In extreme cases, the mower is simply placed on 2 stools, and then the knife itself is removed. To do this, it must be blocked (for example, with a crowbar or wooden beam) and unscrew 2-3 bolts one by one from below. You should be careful, as the washers will also come off.
After removing the knife, carefully inspect it for chips and burrs that occur when the mower hits a stone or other solid object. If there are any, you need to remove them by grinding. The easiest option is to grind off the entire edge. However, if you do this on one side of the blade, you will have to grind down the same amount on the other, regardless of whether there are any chips. This is all done because of proper balancing. Further, the sharpening of lawn mower knives begins.
To edit and turn the cutting edge you will need:
- Bulgarian;
- vice;
- drill with an adapter for sanding paper (discs);
- file;
- sandpaper (sandpaper) for about 250 grit.
It is necessary to start by leveling the cutting edge (if it has not been ground). For this purpose grinder will do with a grinding wheel or a coarse grindstone (up to 400 grit).
The standard sharpening angle is 30 ° (guided from one side only).
However, it is recommended that this information be clarified in the mower's instruction manual. Some manufacturers make an edge on a lawn mower knife at 20-25 °. In this way, greater sharpness is achieved, but the allowable wear before re-sharpening is reduced.
How to sharpen a knife
The simplest and effective method how to sharpen lawn mower knives is to use a drill with an adapter for sanding discs. It is not worth counting on "factory sharpening", since it is performed using a diamond disc, but it is possible to restore the cutting edge using this method in 5-10 minutes.
The disc is selected with a fine grain size, in the range of 800-1500 grit. To sharpen a traditional knife, you need 4-5 of these skins. It is imperative to keep an eye on the balance when sewing edges. To do this, it is enough to hang the knife on a rope, passing it through the central hole for fastening. If he does not deviate to any of the sides, everything is in order. Otherwise, you need to lightly walk again with the sandpaper on the opposite side to equalize the weight.
After sharpening with a disc, all that remains is to finish the cutting edge of the blade. Experts recommend using sharpening stones with a very fine grain size for this, ranging from 1.5 to 4 thousand grit.
You will have to spend at least 15 minutes on each side of the knife, clearly maintaining an angle of 30 °. To achieve the best results, the most top part the blade is rounded. It should be borne in mind that with the final eyeliner, the angle changes by more than 2-3 times. First, a transition is made from 30 to 35 °, then up to 40 °. Literally 2 passes after the change will be more than enough. This shape of the blade is made for greater resistance to burrs.
The trimmer blade (referring to the electric powered lawnmower) is sharpened in a slightly different way. There you will have to use only a file or a diamond sharpener. Perfect option- a grinding machine with a diamond-coated disc. But as a rule, do-it-yourself knife sharpening for an electric lawn mower is not done. This is done by qualified craftsmen using special equipment (laser hemming is performed).
Editing a cutting edge after damage
If part of the cutting edge has been damaged after being hit by a stone or some metal part, but the knife itself was recently sharpened, then the most ordinary musat will help to correct the situation. It is advisable to use high-quality variations of it from ceramics, and not from steel or aluminum coated with an abrasive material. Even the musat used for straightening kitchen knives will do. The only caveat is that the walls of the tool will wear out pretty quickly. That is, it is better to use a separate device for straightening the edge of the lawn mower knives.
You should not expect that the first time you will be able to achieve perfect sharpening of the blade. The most frequent problem that newbies get into is withstanding correct angle at 30 °. For these purposes, the Lansky Stone (Coarse Grain) Machine is useful. This is a manual machine that allows you to set a certain angle when moving. whetstone and maintain it throughout the entire leveling / sharpening process. Such a set is relatively inexpensive, and a set of stones is enough for at least 20-30 sharpenings.
Dull lawn mower blades can be sharpened easily with an abrasive bar or file, but severely damaged blades should be sharpened on a sander bench. The store's customer service can do this for you or tell you when it's time to change your lawn mower blade.
A mower blade that has nicks, dents, or burrs from hitting stones and branches is not good for your lawn. The dull blade tears the grass instead of cutting it cleanly, making it more susceptible to disease. To sharpen a blade that is in fairly good condition, simply grip it in a vise every couple of weeks and drag your touchstone along the cutting edge, making sure that your angle matches the factory bevel. (Always disconnect spark plug wires before removing the mower blade or doing any Maintenance mowers.)
If the blade of a lawn mower knife is severely damaged, it must be sharpened on a sander bench or it may need to be replaced. The store service can sharpen it for you or suggest a new knife. But if you have your own sander, it's easy to do it yourself.
Start by sliding the lawn mower blade back and forth, straight with the cutting edge, perpendicular to the abrasive disc, to grind away any dents and nicks. This will give you a blunt but straight edge. Then, using shims, holding the blade at the angle of the existing chamfer, start grinding the chamfer of the blade until you have sharp edges.
Finally, check to make sure the blade is balanced: a mower blade with an unbalanced blade can damage it. This can be done in a workshop or lawn care service. But you can do the balancing yourself: by placing the blade on the balancer and see - if one side goes down, then you need to remove a little steel from this end (but not from the cutting edge!) To make it lighter. Once the blade is balanced, screw back the mower blade and you are ready to tread on tall grass.
You will need sharpening of knives for lawn mowers in any case, regardless of which lawn mower you use in the country or in the area near your country house... There are several types of lawn mowers: hand trimmer, brushcutter, and self-propelled lawn mower.
All types of lawn mowers have knives that are set in motion in a variety of ways. A mechanical lawn mower begins to work by pushing it along the site, an electric lawn mower is equipped with a motor that works from electrical network, and the motor of a gasoline lawn mower needs to be refueled with gasoline. Each type of lawn mower has pros and cons, and the choice of lawn mower is necessary depending on the area of the site, the type of grass and the size of the lawn.
Whichever of the following units you use, sharpening lawn mower knives is a procedure that will have to be regularly addressed. Well-sharpened lawn mower blades will provide even mowing, cutting, not pulling out the grass by the roots, easy and fast work to care for the site. A worn-out blunt knife with jagged edges from stones and sticks overloads the engine, which can affect the durability of its operation. Sharpening lawn mower blades on time will extend the life of the entire machine.
Lawn mower knife sharpening - service prices
Prices for lawn mower knife sharpening services in our workshop are optimal. Sharpening a lawn mower knife is less expensive than buying new knives. Our workshop is engaged in sharpening knives for lawn mowers in Moscow.
Sharpening a lawn mower knife is a complex process. It is highly undesirable to conduct it at home: firstly, you will need special equipment, and secondly, it is very easy to ruin the knife with poor-quality sharpening. For the correct sharpening of the knife, it is necessary to maintain the desired sharpening angle on both sides of the blade, adjust the balance of the knives. Sharpening of a knife for lawn mowers is carried out on professional equipment. The specialists of our workshop will quickly and efficiently return your knives to working condition. The Blade workshop sharpens lawn mower knives and other household tools.
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