How to unscrew a knife on a lawn mower

How to Replace a Lawnmower Blade. Bosch

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.

How to Remove a mower blade. Technique and no special tools

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 out with a smooth movement from the 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 that remained after sharpening.

unscrew, knife, lawn, mower

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.

Reasons for removing the knife

Common reasons for removing or replacing a cutting element are as follows:

  • The knife is dull;
  • The element is bent and deformed;
  • Chips and cracks are visible on the knife;
  • The blade has worn off and thinned.

Lawn Mower Repair : How to Remove Lawn Mower Blades

When the knife is dull, bent or deformed, the lawn looks untidy after mowing. Competent sharpening will correct the situation.

Professionals advise to carry out the procedure once a year. It is better to do this in the spring, before starting work. If the cutting elements become blunt faster, then sharpen them more often.

If chips, cracks are visible on the blades, or it has sharply worn off and become thin, then replacement is necessary in this case. There is no point in sharpening such a tool. In addition, the blade can break at any time and fly out from under the body of the machine, injuring people or animals that are nearby. Such a device can also damage the engine. It is allowed to change an element to a similar model. The characteristics of the knife are indicated in the instructions.

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How to remove a knife from a lawn mower

The disassembly process depends on the type of lawn mower, but before starting work, make sure that all safety rules are followed.

An electrically powered machine must be de-energized.

On a gasoline powered car, the spark plug cap is removed first. It is important to prevent fuel leakage, therefore the fuel tank of the unit must be empty. It is possible to close the fuel cock by first installing a tight-fitting rubber membrane under the cap. After that, the gas hose is pinched, designed to remove the crankcase waste. Otherwise, there is a risk of oil spillage. It is necessary to constantly check the instructions to avoid possible complications.

The blade is attached in two ways: a single bolt in the center of the structure through a shaped washer or a pair of bolts that are attached to a pin or centering hole. The bolts are unscrewed in a clockwise direction. During this it is important to secure the cutting parts of the mower to avoid injury. For this, a wooden beam with an emphasis on the ground is suitable.

How to safely remove the cutting blade from the mower

Bosch Rotak 37 LI how to change the blade on a lawn mower

Bosch Rotak 37 LI how to change the blade on a lawn mower.

Tatyana65, I have a Honda lawn mower, it is now in its fourth year. A detailed annotation on sharpening the knife is attached to it. larix wrote everything correctly. Although it is safer and more convenient to remove the knife, which, by the way, is attached with 2 bolts. Check balancing by “hanging” on a screwdriver.

Naturally, you should not, according to your ability, run into pebbles and other objects. this greatly spoils the knife.

How to Remove a Knife From a Lawn Mower Video

How to Remove a Lawn Mower Knife

How to remove a knife from a lawn mower Now 04/27/2018 01:11:46 Sharpening of knives from a lawn mower So this problem has arisen. Tell me. and you yourself

Sharpening knives at a lawn mower

So such a discrepancy arose. Tell me. do you sharpen knives yourself? Something intimidated me. they need not only to sharpen, but also to do balancing. How? No, theoretically I figured it out, but practically. well, nothing. Or is it generally better to hand over to a metal repair shop and there they will perfectly sharpen and balance? Or is it better to go to a service workshop? How are you doing?

Tatyana. The clamping screw must be unscrewed counterclockwise: 99.9% of lawn mowers (German, Italian, American, Swedish) have a right-hand thread. Only it is better to twist not with pliers, but with an adjustable wrench, and even better. with a socket head.

Sharpening a lawn mower knife from Lenfilm studio

We tried our best. If you are not very happy, then take a look at our website. There we sorted out the “flights” in detail.

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How to sharpen a lawn mower knife?

How to sharpen a lawn mower knife yourself? Sharpening of knives for lawn mowers is quite within the power of most owners of these devices necessary in a summer cottage.

Lay down or (if large) gently tilt the mower on its side. Put on gloves, grab a brush, and carefully clean around the knife to remove clippings and debris. If the knife is dull, it must be removed. Unscrew the bolt that secures the knife with a socket or open-end wrench. The bolt is located in the middle of the knife. The knife is a metal bar about 50cm long and about 2.5mm thick.

How to sharpen a lawn mower knife? It would be nice to clamp it in a vice and file it. In reality, often only an abrasive wheel or a bar for sharpening knives is at hand. Note that the cutting surface of the knife is hardened, so your impact should be minimal. It is necessary to process with a bar or a small file only the really damaged edge of the surface. If the knife is bent, place it on a massive, obviously flat surface (a piece of railroad track, for example) and straighten it with a hammer. Remove large burrs with a file, then work the blunt fragments with a bar starting from the center of the knife and moving towards the edge. The movement of the bar should be “away from you”. Have you ever seen how a scythe is sharpened? This is approximately how you should act.

When finished, put the knife back in place and tighten with the bolt. Excessive efforts at the same time to nothing, subsequently you will have to unscrew it more than once. Lawn mower knives are usually sharpened in early spring before the first mowing. In the future, if you are cutting grass on an area of ‚Äč‚Äčabout 2-3 acres (200-300 sq. M.) During the season, you do not need to perform any actions with the knife.

You can also use the currently widely used electric grinders, but be careful when using them! With the help of such a machine, you can very easily grind off too much metal and thereby spoil the knife irrevocably. Practice first with kitchen knives, old scissors, or steel strips to get a feel for the force that needs to be applied to the part while sharpening. A knife that is heated during the sharpening process must be periodically lowered into water, this will harden it a little, in addition, a wet grinding wheel removes excess heat, preventing the workpiece from being overheated.

The mower does not cut the grass

  • The knife is blunt or broken. Sharpen it with a file, an angle grinder, on a grinder (you need a flat-cylindrical grindstone) or on a machine (or drill) with emery wheels. Check torch balance.
  • The cutter itself is not set correctly. Set a gap in the cylindrical mower between the rotating cylinder and the blades of the knife equal to the thickness of the sheet of paper.

How to remove a knife from a lawn mower

Cutting elements in lawn mowers are important components that require special care. Over time, the blades deteriorate. In this case, they are supposed to be sharpened or replaced. Before removing the knife from the mower, the owner of the site must perform actions that will protect him during work.

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If you are doing the work with a file or abrasive bar, then sharpening is done from the center of the knife to the edge. The movement of the instrument is “away from oneself”. After completing the work, it is necessary to check whether the balancing of the lawn mower blade has changed.

The sharpened knife can be installed on the lawn mower and start mowing the lawn.


Sharpening of cutting elements is organized as required. Many people ask the question: “Does a new knife need sharpening?” The answer is no. These elements are sharpened at the factory. After purchasing garden equipment, it can be used without additional work on removing and sharpening the blades.

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

Machine tool

The machine will help you get the job done quickly and without much effort. The main thing in this business is not to achieve too sharp edges. If you sharpen them as thin as a razor, then there is a great risk of chipping and breaking.

While working, it is important to keep the correct angle and remove the metal from the blades in the same amount. The machine does not eliminate the need to edit the edges with sandpaper.

Purpose and requirements

The purpose of the mower cutter is to cut the grass evenly and neatly in large quantities. In one session, when mowing one hundred square meters of a plot, you can collect tens of kilograms of grass. If the lawn mower has the function of shredding (mulching), such a knife should also chop the grass. The mower’s cutter is designed so that its blades create upward thrust for the grass that has just been cut. She carries this herb into the collector.

The best alloy for a mowing knife is stainless steel. over, it must have a hardness of at least 55 units on the Rockwell scale. A lower hardness value will quickly dull the cutter. especially when cutting weeds and trimming bushes. Since the cut grass contains not only moisture, but also other active components, ordinary steel would quickly become covered with a brown coating after the very first mowing session. Stainless steel, creating on its surface a chromium oxide that resists corrosion (chromium is also included in the list of alloying additives), does not allow the knife to rust.

Important! In addition to being tough, the cutter must also be sturdy. If, during work, he stumbles upon a stone, then it should not fly apart.

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