How to sharpen lawn mower blade without removing it

Is it possible to sharpen the mower without removing the blade. Sharpening the blade! The finer points of working with a lawn mower. Lawn mower blade sharpening by hand

A messy lawn right after mowing. a sure sign that the mower’s blade is blunt. There are two possible solutions: sharpen the blade yourself or take it to a service center. Let’s start with the first option.

It is better to remove the blade for convenience (read more in our instructions). Before turning the mower, don’t forget to drain the fuel from the tank and oil from the crankcase. Alternative way. Put the mower on a solid frame or at least two stools to “get underneath” it.

Grinding by hand

If the blade is not too blunt, it is enough to mend the edges with a flat file.

  • First remove the rust (if there is any) with a wire sponge or brush.
  • Do not cut as sharp as a razor. Remove any burrs or dings.
  • Try to keep the original sharpening angle and sharpen both blades evenly. Otherwise, imbalance will occur and the blade will wobble from side to side. As a consequence. fast bearing wear and motor change.

To check the balance, suspend the blade with a pencil or nail in the center hole. Next, see if one of the sides outweighs the other. If so, the heavier side needs another file.

What is the problem??

Lawn mower blade rotates at high speed. It has a center hole for the fastener, and both parts from this hole must have equal weight for even rotation. What happens when an inexperienced user starts sharpening?

  • In the sharpening process, more metal is removed on one side than on the other.
  • An imbalance occurs: the blade “beats” as it rotates.
  • Unbalance leads to fast bearing damage: the lawnmower needs to be repaired.

If you have decided to sharpen the knife yourself, it is necessary to keep in mind that it must be done accurately, slowly and with taking into account the nuances that we have noted above. Here are some tips to get the job done.

Necessary tools

You’ll need the following tools to level your mower blade:

  • angle grinder;
  • hammer and anvil;
  • coarse-grained sandpaper and a sharpening stone (bar-shaped) with 200-1500 grit
  • vise;
  • ruler;
  • a crowbar or a wooden stick and a pair of stools;
  • A drill with a sanding paper head or sharpener (discs).

This list is definitive. Some tools and appliances may not be necessary.

Cleaning and dressing

When the knife is removed, first of all you need to clean it from the adhered dirt and hardened grass juice. The easiest way to do this is to use a metal trowel. The blade should be clean on all sides: not to a metallic sheen, but without the smallest sticky fragments.

Often hard objects such as stones and wood chips enter the work area and cause the blade to deform quite noticeably. Most blades themselves are not straight, but the cutting edge and the strip at 10-15 cm from it should be inspected on the presence of local bumps and curvatures. This can be done with a short straight ruler.

You may straighten the blade with an ordinary hammer that has a slightly rounded edge. The blade is placed on a flat, solid support (anvil), then the metal is given the correct shape by light blows. You need to straighten the blade, starting from the edges of the curved area, gradually moving toward the center. A curved blade body is a minor problem, but it is very important that the cutting parts be straightened into one straight line for the trimmer. You should also check the ejector blades, which are often bent on impact. If the blades are bent at different angles on the different shoulders of the blade, it will impair airflow and the mowed grass will not be properly mulched.

Dislodging the edges

If the blade has not been sharpened for a long time it is very likely that it will get chipped. They must be eliminated by aligning the blade edge at an even angle over the entire cutting length. Note that there can be several edges on each side, in which case the lawnmower will have several cutting planes.

Lawn mower blades are unilaterally sharpened, with the tip usually pointing upwards. In order to get the bevel at the right angle, you should use an electric sharpener with a carborundum stone, or if you do not have one, a fine file. It is very important to remove the metal evenly from both blades. So keep the same pressure and at least count the number of passes on the sharpener.

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Small deviations of the sharpening angle are not critical, but the flatter the chamfers are, the longer the blade will last. When shaping the blade, always move it against the grain to avoid large burrs and chips. Do not use an angle grinder for pre-sharpening. overheating can worsen the quality of the metal. However, it is possible to fit a flap wheel or a disk under the sandpaper on the angle grinder.


If the knife has not been sharpened for a long time, it is likely to have chipped blades. You need to get rid of them by bringing the blade edge at an even angle along the entire length of the cutting area. Note that there can be several edges on each side, in which case the lawnmower has several cutting planes.

Lawn mower blades have a single-sided sharpening pattern, with the tip usually facing upwards. To derive the descent at the desired angle, you should use an electric grinder with a stone made of carborundum, or in the absence of such. a fine file. It is very important to remove the metal evenly from both blades. Therefore, keep the same pressure and at least estimate the number of passes of the sharpener.

Small variations in sharpening angle are not critical, but the smoother the bevels are, the longer the blade will last. When shaping the blade, it always moves against the grain to avoid the formation of large burrs and burrs. Do not use an angle grinder for pre-sharpening, since overheating may impair the quality of the metal. However, it is possible to fit an angle grinder with a flap wheel or a disk under the sandpaper.

Blade sharpening

The purpose of the actual sharpening is to eliminate fine chipping of the edge and bring the bevel to one straight plane. A “file” on the blade causes a rapid drop in sharpness, and a rounded trigger causes too much stress on the cut stalks. In addition, a blade with a rounded shape gets dirty much faster.

Sharpening the blade is best done with a flat sanding stone with a grit size of about 400-600 grits, more “delicate” stones do not make much sense. Soak the stone in soapy water for 10-15 minutes and periodically wet it during sharpening. Sharpen the knife also on the grain with a slight pull of the bar from the center of the sharpened area to the edge.

When sharpening, try to keep the stone in the same position to maintain a constant angle. As with the descents, sharpening should be carried out so that the same amount of metal is removed on opposite blades. This condition, however, does not have to be strictly observed when sharpening four-blade knives.

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The electric motor is powered by electricity and has a limited operating radius and depends on the length of the wire. Allows the operator to work only in dry weather to avoid electric shock. It is necessary to take care that the cable is not cut accidentally, because the blades are very sharp and rotate at high speed.

The most mobile lawn mowers with a gasoline engine. They have no limited working radius, and the electric shock won’t happen. Here is the main thing. the correct inclination angle of the lawnmower to get the fuel evenly into the engine, an angle of no more than 30 degrees. Mowing steep slopes should be done with care, assessing the surface of the slide to be mowed in order to protect the motor as much as possible from damage.

We do the following sharpening jobs:

  • Approximate price 400
  • 300 approximate price
  • Approximate price 200
  • Approximate price 150
  • Approximate price 350
  • Approximate price 250
  • Approximate price 250
  • Approximate price 250
  • Approximate price 450
  • Approximate price 225
  • Approximate price 300
  • The approximate price is 220

Although the blades of the lawnmower are made of quality steel, they need to be resharpened from time to time. Fortunately, this does not require special skills and equipment, and today we will tell you how to sharpen the blade of the lawnmower yourself, without deteriorating the quality of the metal.

You can cut excess grass from the lawn even if the mower blade has obviously blunted edges. However, in doing so, the shoots will split lengthwise, turning into a fringe. Grass will be withered after a few days and will be painful for weeks. The cut has to be straight and accurate, then it will heal in a few hours and the lawn will always be a rich green. This requires the blade to be sharpened almost perfectly.

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Left: Grass cut with a blunted mower blade. On the right: Grass cut by a sharp blade

How to remove the blade from the lawnmower

Before you start to dismantle the mower partially, you need to protect yourself and the lawnmower. While an electric lawn mower can be unplugged easily, petrol lawn mowers need a certain amount of preparation. The first thing to do is to remove the spark plug cover. Next, you should exclude fuel leaks, that is, either to drain the tank, or put a sealed rubber membrane under the cover and block the fuel tap. The mower should only be turned to the side of the handle, unless otherwise explicitly stated in the instruction manual. Before flipping the mower over, remember to squeeze the crankcase exhaust hose to prevent oil spillage.

Lawn mowers use different configurations of blades. In the simplest case, it is an ordinary two-blade plate of complex shape, but the blade can also be composite. the upper blade is designed to mulch the mowed grass. There are also four-blade blades that can be either compound or on a common base.

The blade can be mounted either with a single bolt through a washer, or with two bolts resting on a center hole or pin. In any case the thread on the bolts is right-handed, so unscrew it counterclockwise. To block the shaft from rotating, put a block propped in the ground under the blade. It is desirable to memorize or mark the position of the blade(s), so as not to mix up anything during reassembly. Temporarily install unscrewed bolts in vacant holes.

Cleaning the knife before sharpening

Clean knife thoroughly before sharpening. Plant sap and small grass particles accumulate on the steel strips. The sap will harden over time and turn into a hard crust. Do not wash the blades, it is best to pick up a sharp metal scraper in the garage or apply a scratch brush.

It is not necessary to polish the cutting element of the machine to a shine, the main thing is to remove the adhered debris. After that it is necessary to improve the knife by straightening it and removing all the irregularities. Bumps are caused by hard chips and stones on the blade. The correct option in this case is to work with a hammer. With the help of this tool and a flat work surface on which the knife is placed, all local curvatures can be corrected.

Cleaning the knife before sharpening

Experts advise to start smoothing the blade from the edge, gradually moving to the middle part. The steel band should be as flat as possible afterwards. Only then will it be able to perform its function, creating an air flow that carries the grass into the crop tank.

Finishing with an angle grinder

Knife dents can be leveled with a hammer on a flat hard surface.

If the knife is significantly damaged, it is easier to cut the cutting edge to the required distance and sharpen again. For cutting, you need to measure with a caliper or other marking device with the required accuracy.

Keep the balance of the blade in mind when doing this. Carry out the trimming operation on both sides by the same amount. After trimming, surfaces can be sharpened. It is more convenient to perform the sharpening operation with the tool fixed by moving the knife in a circle.

In the presence of the speed controller on the angle grinder, it is desirable to choose the optimal mode of the tool, so as not to overheat the cutting edges.

To sharpen the blade, change from a cutting wheel to a sharpening wheel, fillet at a proper angle until a sharp edge is formed. Grind to the required quality by hand using a stone or emery cloth.

Finishing with an angle grinder

Knife dents can be leveled with a hammer on a flat hard surface.

If the knife is very damaged, it is easier to cut the cutting edge the required distance and resharpen. For trimming, measure out the required size with a caliper or other precision measuring device.

Keep the balance of the knife in mind when sharpening. Trimming should be performed to the same extent on both sides. After trimming, the surfaces can be sharpened. It is more convenient to grind with the tool still mounted by moving the knife in a circle.

If there is a speed regulator on the angle grinder, it is advisable to choose the optimal mode of operation of the tool, so as not to overheat the cutting edges.

For sharpening, it is necessary to change the wheel from cutting purpose to sharpening one, remove metal at the required angle until a sharp edge is formed. Sharpening to the desired quality by hand with a stone or emery cloth.

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Sharpening of cutting edges as needed. Many people wonder “does a new knife need sharpening?”. The answer is no. These elements are sharpened at the factory. After the purchase of the garden equipment, it can be used without additional work to remove and sharpen the blades.

There are two ways to sharpen the cutting element of a lawnmower:


In the first case, the work is organized if the blades are in relatively good condition and are only slightly blunt. Usually such a sharpening is applied if the owner sharpen the cutting elements of his garden tools several times during the season. If this is the case, it will be enough to go over the edges with a file and correct them.

During the work roundings of the knife, roughnesses are removed. It is important to keep the factory rake angles and the escapement. Grind both sides (blades) evenly. The sharpener should be held in the same position. Do not allow for unbalance, which will prevent the blades to work smoothly. Such a problem will lead to rapid wear of the assemblies (bearings).

Sharpening with a file

After the basic sharpening, the edges must be dressed. This is to remove the smallest breakage. It is best to use an emery cloth with a grain size of 800 grits. Dressing consists in a slight displacement of the paper along the plane of the escapement.

Note! A file can be used instead of a file. Soak it in water and soap for a quarter of an hour before proceeding. It is also permissible to slightly moisten the tool during operation.

Using the machine

The machine will help you to cope with the work quickly and without great effort. The main thing in this case is not to achieve too sharp edges. If you sharpen them as thin as a razor, there is a great risk of chipping and breaking.

Sharpening on the machine

During the work it is important to keep the right angle and to remove the metal from the blades in the same amount. The machine does not eliminate the need to straighten edges with emery cloth.

Edge dressing

When the blades are sharpened, they need to be corrected. This is done with a piece of waterproof sandpaper with a grit of about 600-800 grits. The paper should be moistened with water and rolled into a cylinder 100-150 mm in diameter.

The purpose of straightening is to remove the smallest burrs and chips that can wrap the thinnest edge of the blade. Rolled in a cylinder, the sandpaper should be slightly pressed to the plane of the descent and pulled through with a smooth movement from the grain. It is also recommended to make a smooth displacement from the center to the edges.

All manipulation was done with only one side of the blade when bringing out the descents and sharpening. During straightening the blade is also machined on the back side. Here the paper is pressed almost flush against the body of the blade, but with a slight tilt toward the edge. The paper contact pressure during straightening is very low, but you have to make many movements to eliminate big ribs on the shiny tip, which are left after sharpening.

For your information: You can also sharpen the blade of a lawnmower using a chopper similar to an ordinary hand-held mower. This, however, requires a special device. a headstock, as well as a specific skill. But with this sharpening method you don’t need to balance the blade.

Checking the balance

Before putting the blade back on, make sure that its shoulders have at least approximately the same weight. Otherwise it causes vibration during operation, which is not good for the durability of the spindle.

The balancing is done mainly for the two-sided single and compound knives, the four-blade knives are not as prone to imbalance. To test the blade, clamp a smooth bar in a vice in a horizontal position. The blade is put on it through the hole in the center, and then attempts to set it strictly horizontally. If one of the arms weighs considerably more than the other, the knife will steadily rotate to one side.

Equal weight of the arms is done by grinding a small amount of metal from the back of one of the arms of the knife. It is not necessary to achieve a super-precise balancing, but the blade should stay at least for a few seconds in a strictly horizontal position. When the balancing is done, you can put the blade back in place and finally refresh the look of your lawn.