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In this video, This Old House landscape contractor Roger Cook shows how to convert a dull blade and cut grass cleanly.

Steps to Sharpen Mower Blades

  1. Disconnect the spark-plug wire from the spark plug to prevent accidental starting.
  2. Tip-up the lawnmower with its spark plug pointing vertically.
  3. Put on a leather work glove and grab hold of the lawnmower blade.
  4. Use a ratcheting socket wrench to remove the nuts holding the blade to the mower.
  5. Remove the blade from the mower.
  6. Clamp the blade in a vise and use a metal file to sharpen the cutting edges of the blade.
  7. Chuck a blade-sharpening stone into a drill/driver and use it to sharpen the lawnmower blade. Be sure to keep the stone's plastic guide against the rear of the blade.
  8. Sharpen the lawnmower blade using a bench grinder and get it “butter knife sharp.”
  9. Repeat to sharpen the opposite end of the blade.
  10. Set the sharpened blade onto a blade balancer. If the blade is out of balance, file or grind a bit more steel from the heavy end.
  11. Use a putty knife to scrape away any matted grass clippings from the underside of the mowing deck.
  12. Reinstall the blade, firmly tightening the nuts with a ratcheting socket wrench.
  13. Lower the mower and reattach the spark-plug wire.