Sharpening Mower Blades

How often do you get a new razor blade? You wouldn’t scratch the hair off your face or legs with a blade you’ve used for eight months. Why would you think your lawn is any different?

When was the last time you sharpened your lawn mower blade? If you can’t remember, it’s time to do a little maintenance. If you can remember, it’s still probably time: Your grass will look better when you sharpen your mower’s blade at least a couple times a year.

Just like that dull razor doesn’t cut hair very well, a dull blade won’t cut grass cleanly. Those dull blades yank grass and leave an uneven edge that doesn’t heal as quickly as a clean cut. Those ragged edges also make your lawn prone to fungal infections, too. Grass cut with a sharp blade is healthier and looks better. As a bonus, it’s easier on your mower to cut more efficiently.

You don’t need to be a mechanic to sharpen your lawn mower’s blade. Spend 10 to 15 minutes sharpening your blade with these simple steps:

  1. Remove the spark plug wire: Play it safe and pop the plug wire whenever you’re working on your mower.
  2. Note blade orientation: Skip the guesswork – and repositioning your blade when it won’t cut – by taking note of how the blade is mounted to the arm. Using chalk or paint, mark the bottom of the blade before removal.
  3. Remove Blade: Using a wrench, unscrew the bolts that hold the blade to the motor arm. You’ll likely need a long-handled wrench to get the torque necessary to remove the bolts. If you can’t generate the torque necessary to remove the bolts, try fitting a pipe over the wrench handle to increase its length and give you more leverage.
  4. Sharpen Blade: Follow the existing bevel on the blade’s cutting edge. Use a metal file to hone the cutting edge. File from the inside out, using moderate pressure. Don’t get carried away: Blades are generally manufactured with soft metal and are typically sharpened with 25-50 strokes. Your blade doesn’t need to be razor-sharp to do the trick.
  5. Replace Blade: Use your markings from before removal to orient the blade properly, and attach bolts. Make sure it’s as securely fastened as when you removed it, which may require use of a pipe to fully tighten the bolts.

After mowing, if your turf’s appearance doesn’t improve, you may have a thatch problem. Read our guide to de-thatching to determine if it’s time to tackle that chore.