How to Sharpen Lawnmower
No need to pay someone else; you can do it in about 15 minutes
A sharp blade is better for the looks and health of your grass, so it’s best to sharpen it twice during each mowing season. That may take you 30 minutes the first time. But once you’ve learned how, you’ll cut that time in half.
Mark the blade
People often reinstall blades upside down and then go nuts trying to figure out why it won’t cut. To prevent that, mark the face-down side with a blast of spray paint before you remove it.
1. Disconnect the spark plug
Yank off the plug wire to prevent accidental firing of the engine. That’s unlikely, but possible. Don’t forget to reconnect the wire before you try to start the engine.
2. Remove the blade
Turn the mower on its side with the air filter and carburetor side up. That prevents oil and gas from dripping into the air filter. Wedge a block of wood against the deck to lock the blade in place as you unscrew the bolt that secures the blade. A squirt of penetrating oil helps to free a stubborn bolt.
3. Sharpen the blade
Secure the blade with a clamp or vise, top side up. Then get to work with a metal file. Hold the file at the same angle as the bevel on the blade to avoid changing the cutting angle. Apply pressure as you push the file forward; apply no pressure on the backstroke. Don’t go for razor-sharp. Butter-knife-sharp is good enough.
4. Check the balance
An out-of-balance blade causes vibration and extra wear on bearings. So hang the blade on a nail. If one side dips, file it to remove some metal and balance the blade. Reinstall the blade and cut some grass.