How to Sharpen a Rotary Lawn Mower Blade

If you've noticed that your last mowing job left some uneven edges and jagged blades of grass in your yard, you might want to take a close look at the sharpness of your blade. A dull blade will make your mowing results sloppy at best, and at worst, it will overwork the engine and lead to a premature death for your mower. Make sure you sharpen your blade as needed by following the steps below.

Difficulty: Moderately Easy

Instructions

Things You'll Need:

• Lawn mower
• Wrench
• Vice clamps
• Coarse file
• Smooth file
• Work bench or stable surface

1. Open your lawn mower's protective case and disconnect the spark plug wire. You may want to consult your mower's manual for a parts diagram if you've never attempted this on your mower before. Disconnecting this wire will make it impossible for the mower to accidentally start while you're removing or reinstalling the blade.

2. Tip the mower on its side, being careful not to spill any fluids like fuel or oil. Use a hand wrench to remove the bolts holding the blade into place.

3. Use vice clamps to clamp the blade onto your work bench or another strong, stable surface.

4. Examine the angle of the blade edge and study it closely if you're inexperienced with blade sharpening. It's important to sharpen the blade at the original angle in order to keep it in balance. Start sharpening by using the coarse file and pressing into the blade edge with significant pressure as you run the file along the blade. Take your time and maintain the angle as you give each individual blade about 20 passes with the coarse file.

5. Switch to the smooth file and finish sharpening the blade in the same manner as you used the coarse file. Be sure to maintain that same blade angle as you work.

6. Remove the blade from the vice clamps and slide it back onto the shaft on the bottom of the mower. Use a wrench to replace and tighten the bolts, then stand the mower upright and replace the spark plug wire.

Tips & Warnings

• Blades that are heavily nicked or very dull can be extremely difficult to sharpen. These blades will often be impossible to restore to a fine edge. If your blade is in really bad shape, it's probably your best bet to just replace it.
• Even dull blades can be dangerous. Watch your fingers and work carefully as you sharpen; filing blades requires you to run your hands quickly past some very sharp surfaces.