How to Sharpen a Lawn Mower Blade

Learn how to sharpen your lawn mower's blade with these easy steps.

By: Debbie and Mark Wolfe

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Sharpen Your Lawn Mower Blades

If you mow your own grass, you need to know how to sharpen the blade on your mower. A sharp lawn mower blade saves time and energy while mowing, ensures a clean cut, and even helps to minimize the spread of lawn fungus.

Remove the Old Blade

Follow these steps to safely remove the old blade: Disconnect the spark plug. Tip the mower up on its side. The side with the carburetor and air filter should be on top. Block the blade with the piece of 2' x 4' or place a piece of 3-inch pipe through the side discharge and over the blade to hold it in place. Use the wrench to remove the bolt which holds the blade in place. Set the bolt and washer aside where they will not be lost.

The Old Blade Still Has Plenty of Life

You can tell if the blade is worth the time to sharpen or not. Once its removed, take a look at its thickness; this will let you know if you can still sharpen the blade.

Clamp the Blade to a Work Table

Clamp the blade in the vice in “cutting position”, with the first end to be sharpened extending 3 or 4 inches beyond the jaws of the vice.

File the Blade

Following the original angle of the cutting edge (approximately 30 degrees), and with long steady strokes, use the file to smooth the rough cutting edge back to a flat sharp surface. For quick grinding action, a double-cut file will remove a lot of material fast. For honing and creating a final edge use a single-cut file. Double-sided files are available with one side single-cut and the other side double-cut. When the first end is complete, reposition the blade and sharpen the other cutting edge.

The Finished Sharpened Lawn Mower Blade

Once both sides are sharp, check the balance of the blade by hanging it on a nail through the bolt hole. If it hangs horizontally, it’s ready to reinstall. If one end hangs lower than the other, file a bit more off that end’s edge until the blade balances on the nail. This will ensure that the mower runs smoothly. Re-install the sharpened, balanced blade. Remember to use the 2' x 4' or pipe to stabilize the blade as you tighten the bolt. Reconnect the spark plug wire. You’re ready to mow!