Sharpen Lawn Mower Blade: That’s How It’s Done

Do you have to mow lawn several times before all grasses are cut? The reason? A truncated lawn mower blade and it’s the time to sharpen your lawn mower blade.

In addition to the speed of rotation of the mower, the sharpness of the lawn mower blade is particularly important in order to mow the lawn efficiently, thoroughly and cleanly.

The lawn mower blade can be sharpened by the professional, but you can do it yourself, if you observe a few hints. We’ll show you how to do it right..

The important stuff

  • Lawn mower blade should always be sharp for a thorough and clean cut. If mowing lacks quality, it’s time to sharpen the blades.
  • The lawn mower blade can be ground with a hand file or a wet grinder. It is also important to properly balance the blade after sanding.
  • If you want to sharpen the lawn mower blade, you should definitely follow certain safety precautions, so the mower should not be connected to the power source.

What is a lawn mower blade?

The blade of a lawn mower is a long sharp blade attached to the bottom of the lawn mower. This knife rotates with a high speed and mows the grass.

Lawn mowing knives are usually made of stainless steel or another tough durable metal. Mowing causes the knives to become dull after a while. Then they can either be exchanged or sanded.

What you should know about lawn mower blade

The lawn mower blade is an important part of the lawn mower, which requires regular care. Nevertheless, it is often overlooked, after all, it is tucked on the bottom of the lawn mower.

Before deciding to grind the lawn mower blade, it’s important to understand why the lawn mower blade is so important, and what to consider when sanding.

Why does the lawn mower blade have to be sharpened?

The lawn mower blade should be sharpened, that can the lawn mower function ideally. The efficiency of a lawn mower depends on two factors – the speed and sharpness of its blade.

Only when the lawn mower knife is sharp, the lawn can be cut thoroughly and evenly.

Most lawn mower blades can be ground without much effort. Regular sharpening extends the life and quality of your device.

How often should the lawn mower blade be sharpened?

How often the blade has to be sharpened depends on many factors. This includes:

  • Quality of the blade
  • Size and texture of the mowed lawn
  • Frequency of mowing
  • Storage conditions and care of the lawn mower

Better quality lawn mowers have blades, that rarely have to be resharpened. Even if the lawn is mowed often, the knife will wear out slowly.

Generally, the lawn mower blade should be resharpened if it is noted that the cutting quality of the mower has decreased. It is recommended to sharpen lawn mower blade annually, preferably at the beginning of the warm season.

Which lawn mower blades can be sharpened?

Basically all lawn mower blades can be sharpened, except the ones that the manufacturer warns against it.

Lawn mower blades are steel blades, that can be sharpened and sharpened like any other knife. Depending on which shape they have, they are easier or harder to grind.

If you are not sure how to sharpen your lawn mower blade best, you can contact a specialist or the manufacturer. On the Internet, there are also numerous instructions for different mower knife models.

How can I sharpen the lawn mower blade?

The lawn mower blade should be sharpened in four steps. The process is as follows:

  1. Preparation
  2. Remove the blade
  3. Cleaning
  4. Grinding and balancing
  5. Install the blade

What tools do I need to sharpen the lawn mower blade?

To grind the lawn mower blade, you will need a hand file or wet grinder. But other tools could be also helpful.

  • Hand file or wet grinding machine
  • Vise
  • Cloth to clean
  • Wire brush
  • Protective gloves
  • Safety goggles

What should you pay attention to when grinding the blade?

Lawn mower sharpening is not a difficult task, but you should pay attention to a few hints. On the one hand, it is important to properly disassemble and sharpen the blade, on the other hand, you should follow some safety precautions.

  • Disconnect power supply, remove spark plug, remove the battery
  • The device should not start under any circumstances!
  • Place the petrol mower on it’s side so, that no petrol escapes
  • Wear protective gloves and safety goggles
  • Securely secure the dismounted blade during grinding, e.g. with ferrule or vise

And so, that the grinding succeeds properly and your lawn mower is perfectly operational again, you should note the following:

  • Clean lawn mower blade with a cloth before sanding
  • Grind blade on one side only (top side)
  • Always observe the specified grinding angle
  • Do not take off too much
  • Balance the mower blade to avoid jiggling the lawn mower
  • Secure lawn mower blade securely when installing

Sharpen lawn mower blade: This is how it is done

If you want to sharpen the blade of your lawn mower, you should follow a few pointers. We explain in which steps the lawn mower blade is sanded and what you have to pay attention to.

We discuss what is important in the preparation and what security measures you should take.

In addition, we will show you how to properly disassemble, clean, sand and balance the mower blade.

1. The preparation

If you have decided to grind the lawn mower knife yourself, it’s time to prepare first.

You should prepare a safe work surface, for example a large table, and prepare all the necessary tools. Be sure to wear protective gloves and goggles.

It is also helpful to have the instructions for your device. This section explains how to properly extend the knife bar.

Then you should make sure that the lawn mower can not start. This is incredibly important, because when the blade starts to rotate, you can get seriously injured.

2. Remove lawn mower blade

Now you can carefully remove the knife, according to instructions. It is usually located at the bottom of the device and can be removed without much difficulty.

If there are washers, you should remember the order and put it safely aside. After grinding, they should also be reinstalled.

Then you should fix the blade in a vise. This makes it easier to clean and grind the knife, makes work safer and also gives better results.

Clamp the knife bar horizontally and so that the knife wings are pointing upwards that the cutting surfaces are visible.

3. Clean lawn mower blade

Before you start sanding, the lawn mower blade should be cleaned. Grass and earth remains on the knife bar are not uncommon

With a cloth you can simply wipe off these soiling. If necessary, you can moisten it or use a mild detergent.

Depending on the age and quality of the product, the mower blade may also be damaged by moisture. Rust stains can be removed with a wire brush..

4. Grind and balance the lawn mower blade

When the lawn mower knife is roughly cleaned, you can start sanding. For sanding you should use a hand file.

This allows unexperienced beginners more control over the grinding. In addition, it prevents that too much material is removed.

An electrical alternative is a wet grinder. The use of an angle grinder is not recommended, as this device could remove too much material, make it more difficult to guide and can damage the soft steel due to the heat.

Once you have prepared the grinding tool, you can start. You should proceed with sanding as follows.

  • Grind only the top of the cutting surface
  • Be sure to keep the original angle when grinding
  • First grind with a coarse file, then with a finer one after
  • Grind both blades evenly, do not remove too much material

Balancing the blade is an important step, that should not be forgotten. Because if the knife is out of balance, the lawn mower starts to “yell”, the grass clippings become irregular and the crankshaft bearing can also be damaged.

Whether the knife is properly balanced, you can determine by placing it in the middle of a small increase.

If the mower blade has a hohow tole in the middle, you can balance it on a screwdriver or something similar.

When a lawn mower blade is properly balanced, the weight is evenly distributed and the blade does not lean to one side.

If this is not the case, the knife should be reground, so that both sides are in balance.

5. Reinstall lawn mower blade

Once you have done the sanding and the lawn mower knife is sharp and balanced again, you can put it back in the lawn mower.

The lawn mower blade should be installed according to the instructions for use. The lawn mower blade should be installed with the unpolished surface facing down and the wings facing up.

If any washers or other components have been removed, they must of course be re-installed in the correct order.

Also you can reconnect remote batteries, spark plugs and other energy sources.

Trivia: What else you should know about lawn mower sharpening

What types of lawn mower blades are there?

Lawn mower blades are usually all built the same. They consist of a knife bar, and two wings with cutting surface.

Although lawn mower blades may vary in shape depending on the model, they are generally all ground in the same manner. However, the knives are seldom perfectly interchangeable.

If you are looking for a replacement blade for your lawnmower, you should pay attention to the manufacturer and model. Also, lawnmower blades are different for different types of lawn mowers.

What you should also be aware of is that grinding lawn mower blades can not be easily transferred to grinding knives from other lawn mowers. Grass trimmers, lawn scythe and other mowing machines have their own characteristics, which should be strictly observed.

How do I properly care for the lawn mower?

To ensure that the lawn mower can do it’s job reliably and for a long time, it should be maintained. Besides the mower blade shafts, there are other things to keep in mind.

Before you start cleaning, make sure that the lawn mower is not plugged in, and can not start.

The most important thing is to clean the lawn mower from lawn debris and soil. These contaminants accelerate the corrosion. They can be removed with a cloth, a lot of water and gentle cleaning agents.

Before the winter, the tank should also be emptied with a gasoline lawn mower. It is extremely unfavorable to let the mower with half-full tank overwinter.

For a cordless lawnmower, it should be noted that the battery may be damaged by freezing temperatures.

Of course, the lawn mower knife – the heart of the mower – should be also maintained. As described above, not only sharpening but also cleaning and balancing is required.

How can I mow the lawn without a lawn mower?

If you do not have a working lawn mower available at the moment, there are other ways to get your lawn short.

In addition to the mowing tractor, which is similar to the lawn mower in many things, there are also robotic lawn mowers, which mow the lawn without human help.

On the other hand, there are also devices, that can be guided by hand. These include, for example, grass trimmers.

In recent years, various devices have been developed, with which the lawn can be mowed.

They all have their advantages and disadvantages as well as their own areas of application, which is why they can even be used in combination.

For example, small lawn grasses can be used for areas that the lawn mower does not reach due to it’s size. The robotic lawn mower can be programmed to mow the lawn despite being away, for example while on vacation.


The lawn mower blade should always be sharp, so that the cut can be made evenly and thoroughly. When the blade dulls, the performance of the lawn mower and the quality of the cut diminish.

Lawn mower knives can be sharpened by professionals, but it can also be self-sharpened. For this purpose, it is removed from the mower, ground with a file, and replaced.

It is important to be careful when grinding, to maintain the original grinding angle and to balance the lawn mower blade correctly. As a rule, it is sufficient to sharpen the lawn mower blade once a year as part of spring preparations.