How Do You Sharpen Lawn Mower Blades?

Sharpen a mower blade by disconnecting the spark plug wire, removing the blade, filing the cutting edge, checking for balance and reinstalling the blade. The process can be completed in less than 30 minutes.

  1. Disconnect the spark plug wire

    Disconnecting the plug wire ensures the mower does not accidentally start as you remove the blade. Grab the rubber boot over the spark plug and pull straight out to disconnect it.

  2. Remove the blade

    Turn the mower over to access the blade. Keep the carburetor up to prevent flooding. Note the direction of the blade before removing it. Use an appropriately sized wrench to loosen the retaining nut.

  3. File the blade

    Place the blade in a bench vise, and use a flat file to sharpen the cutting surface. Maintain the manufacturer's angle for the cutting surface. Reverse the blade, and sharpen the other cutting surface.

  4. Check for balance

    Hang the blade over a nail using the center hole. If one side dips, return the blade to the vise, and file a few more strokes on that side. Continue checking for balance and filing until neither side dips when placing the blade on the nail.

  5. Reinstall the blade

    Return the blade to the mower. Make sure the cutting edge faces the same direction as when you removed it. Turn the mower upright, and reattach the spark plug wire.