How To Sharpen Lawnmower Blades

How To Sharpen Lawnmower Blades? Only 7 Simple Steps

One can never argue about the usefulness of lawnmowers in keeping our lawns presentable and stopping grasses from invading our lawn space.

However, the lawnmower’s task of cutting grasses can make its blades dull or blunt in the long run. But we don’t know “how to sharpen lawnmower blades safely”. This is the article where we learn step by step.

Why You Need to Sharpen Your Mower Blade?

It is important to keep our lawnmower blades sharp to guarantee clean cuts and healthy grass. Keeping the blades sharp can add up to the longevity of the lawnmower blades too. If the lawnmower blades are dull, they can pull up the grass from the soil instead of cutting them resulting in a ragged and brown lawn.

To keep the blades sharp, constant sharpening and proper knowledge are highly needed.

Most lawnmower blades last for an average of 100-200 hours of use. If you own a high-quality lawnmower blade, it may last up to 400 hours. So

When Should You Sharpen Lawnmower Blades?

When Should You Sharpen Lawnmower Blades?

I’m glad you asked! The short answer would be after 20-25 hours of usage.

Aside from this time, you may also refer to some indicators below to know if your lawnmower blades need to be sharpened,

  • Look for any dents or scratches.

Minor nicks or dents are common for lawnmower blades and an indicator that they need to be sharpened. However, if these are huge dents, you might need to replace your blades entirely.

  • Examine the grass.

Sharp lawnmowers can cut grass cleanly. If the grass appears to be ragged and torn, then the lawnmower blades have to be sharpened.

If you are certain that your lawnmower blades are up for some sharpening, here is a step-by-step guide on how to sharpen lawnmower blades.

Let’s Start How to Sharpen Lawnmower Blades

Let's Start How to Sharpen Lawnmower Blades Safely

Step 01. Prepare the necessary tools.

You will be surprised how preparing your tools before performing any tasks can save you time and boost efficiency.

To sharpen your lawnmower blades, get ready to prepare the following:

  • File / grinder
  • Vise
  • Personal protection gears (Gloves, Ear protectors, Safety goggles)

Step 02. Remove the blades safely.

Before anything, make sure that the lawnmower will not suddenly turn on by removing the key and the spark plug.

Then position the mower sideways having the air filter and carburetor on the upper sides to keep the oil and gas from entering into the air filter.

Lastly, remove the blade. Unscrew all the connecting bolts and brackets making sure to keep in mind their positions.

Step 03. Sharpen the blade.

There are two common ways to sharpen a lawnmower blade; by a mill file or grinder. Both are viable options but vary with the speed of sharpening.

Sharpen the blade.

Method A.

A mill file is a tool similar to hand files and has an edge for handling. It is single-cut and mainly used for smoothening out work and sharpening mills and other blades. This tool doesn’t use any electricity and is needed to be used manually by hands.

Sharpening a lawnmower blade can take up to 50 strokes of a 10-inch long sharp mill file. For safety, use gloves and safety goggles.

Method B.

For those who like to work with tools and aim for faster results, you can opt to use a grinder. A grinder is a powerful tool that is used for grinding.

It makes sharpening much quicker but they’re more difficult to control. If you are not an expert, there is a tendency that you might ruin the blade or hurt yourself.

For safety, you need to use ear protection, gloves, and safety goggles.

After Deciding Which Method to Use, You Can Now Start Sharpening.

After Deciding Which Method to Use, You Can Now Start Sharpening.

I. Secure the blade in the vise.

Securing the blade in a vise makes it easier to control the filing and avoid sudden blade movements that may cause accidents. If you are new to sharpening, I highly suggest using a vise.

II. Mind the angle.

File according to the original cutting angle. Maintain the angle of the original cutting edge at all times. Most lawnmower blades have 30 degrees angle but it still varies by kind.

III. File or grind until moderate sharpness.

Remember that lawn mower blades don’t need to be razor-sharp to cut the grass cleanly. Very sharp blades can get dull faster and require often sharpening.

Too much sharpening can lead to short blade life.

Step 05. Check the Blade Balance.

Check the Blade Balance.

After sharpening, there is a chance that you have over-sharpened one side than the other. Blades should be sharpened equally and kept leveled. Unbalanced blades can cause vibrations and ruin the blade shaft. To check the blade balance, you can use a nail or a balance checker.

Position the mid part of the blade on top of the upright nail or balance checker. If they are not balanced, sharpen the heavier side more.

Sometimes, the dirt on the blade affects the balancing of the blade. I suggest, cleaning the blade with a steel brush or other cleaning tools before checking.

Step 06. Put the blade back to the lawnmower.

Put the blade back to the lawnmower.

Reinstalling the blades should be an easy task if you already know their positions. Not being able to reinstall the blade properly may result in grass-cutting troubles and potential accidents.

Put back the blade and screw in the connecting bolts and brackets. For the blades, generally, the cutting edge is always at the bottom. Make sure that all components are tightened to avoid loose blades from getting separated from the machine.

Loose components can also make the mower difficult to start and may cause accidents.

Lawnmowers are considered high-risk equipment. In fact, a 2015 report recorded close to 82,000 injuries in that year alone. Making sure that the blades are placed appropriately is the first step towards safety.

Step 07. Reconnect the spark plug.

Lastly, reconnect the spark plug and check for other potential hazards. Sometimes, the only way to see hazards is to see the machine work again. Take your lawnmower for a test drive and examine its performance.

If you didn’t find any faulty components, then your lawnmower should be able to cut grass efficiently again.


Sharpening blades is a crucial practice for lawnmower owners. It keeps the blade more efficient and long-lasting. If your blade is up for some sharpening, keep in mind to prioritize safety.

Prepare your tools beforehand and remove the blades from the mower carefully. If everything is set, you can use a mill file or a grinder to sharpen the blade depending on your preference.

Always check and maintain the original cutting edge angle. Then level your blade and reinstall it properly.

Finally, turn on the machine and examine for any faulty components.

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