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How to Sharpen Lawnmower Blades

There is a step-by-step process to sharpen your lawnmower blade. Along with it, I am also sharing two different methods to do it well.
Sudip Paul Oct 22, 2019


Regardless of the kind of lawnmower you own, it is crucial for you to keep the blade sharp. A sharp lawnmower blade maintains the lawnmower operating smoothly and reduces the amount of time spent working on your grass. Fortunately, sharpening your lawnmower is easy and requires some basic tools. Here is an exclusive look at how to sharpen lawnmower blades.

Sharpening by Hand

Clamp the Blade Safely and Securely at The Work Station

You can safely secure your lawnmower blade using a sturdy clamp or a vise to make it convenient and firm as you work on it. You should secure it in a way that the blade sticks out over the edge of the workbench so that you can correctly work on it.

Use A File to Sharpen the Blade

You should sharpen the blade by running a metal file along the blade’s cutting edge. Use the file to stroke from the inside edge of the blade to the outside edge until you get an apparent shiny edge. Flip the blade over and do the same process on the other side. You should wear a respirator or mask to protect you from the dust and metal particles.

Place It at The Angle of The Factory Bevel When Sharpening

It is crucial that you check the angle of the slope from the manufacturer, which is often 45 or 40 degrees. You should place the file at the angle of the slope of the blade when sharpening. After you finish sharpening, the blade should be relatively as sharp as a butter knife.

Reinstalling the Sharpened Blade

Spray some lubricant on the main bolt to prevent rusting and put the blade back in place on the lawnmower. Put the washers and tighten the bolt completely.

Sharpening Using a Machine

Observe Safety Precautions

Sharpening machines such as bench grinders can fling tiny metal pieces and subtle sparks at high speed, causing potential injury. It is hence essential to ensure that you wear gloves, eye protection, and long sleeves.

Use a Bench Grinder

If your blade has some cracks or dents and you don't want to sharpen it by hand and file, a bench grinder works perfectly. Put the edge back and forth against the grinder’s wheel to sharpen it. Make sure to maintain the original angle of the blade’s bevel as you sharpen it.

Use a Belt Sander as An Alternative

A belt sander is an alternative way to sharpen a lawnmower. You should rub the blade as an angle against the sandpaper to sharpen it via friction.

Prevent the Blade From Overheating by Quenching It

The high heat produced when sharpening the blade with machines can cause the blade to weaken or warp. It is hence essential that you regularly quench the blade with water as its being sharpened. However, you should wipe it dry before you start sharpening again.


It is vital to sharpen the blade regularly as it will make the task easier and quicker as you won’t have to grind a lot to have a sharp edge. In case a lawnmower starts while you are sharpening on the blade, it might cause serious injury. It is hence essential that you ensure you disconnect the power source and spark plug before you start working on it.