How to sharpen your mower blades

How to sharpen your mower blades

Sharp blades are critical to clean-cut grass, a healthy, even lawn, and long-lasting mower performance. Before you store your mower for the season, sharpen its blade as part of the winterizing process — and after every 25 hours of use.

Disconnect power: Unplug your mower for the power supply, remove the battery, or disconnect the spark plug wire to prevent it from accidentally turning on while you’re working.

Empty the gas tank: If your mower uses fuel, drain the tank so gas doesn’t leak when you tip it over to access the blade.

Remove the blade: Carefully turn your mower onto its side, keeping the air filter and carburetor upright. Make a mark on the blade so you know which direction to reattach it when you’re done. Loosen the nut or bolt that holds the blade in place and remove it. While the blade is off, clear out any grass clippings from the deck.

Inspect the blade: Clean off the blade with a damp microfiber cloth and look for signs of serious damage such as dents and cracks. If it’s in bad condition, replace the blade. If it just has some normal wear, proceed with sharpening.

Sharpen the blade: You have several options for sharpening, depending on how much time you have an what tools you have available:

  • Metal file: For this manual method, clamp the blade in a vise with one of the cutting edges facing up. Using a file at least 10 inches long, hold it at a 45-degree angle to the cutting edge and sharpen using a pushing motion in one direction — it shouldn’t take more than 50 strokes to get it sufficiently  sharp. Then rotate the blade to repeat this process on the other end.
  • Electric angle grinder: Clamp the blade into the vise then run the grinder down the length of the cutting edge, making sure to keep the correct angle. Check for even shine after the initial pass — if it’s shinier at one end, adjust your angle. Continue until the blade is sharp. Repeat this process on the other edge.
  • Drill-powered blade sharpener: Place the blade in a vise and fit the blade sharpener to your drill just like a normal drill bit. When you hold the sharpener over the blade, the cutting edge should be pressed up against the stone bevel. Turn on the drill and move the sharpener across the cutting length of the blade for just a few strokes until it’s sharp. Then repeat on the other edge.

Check the balance: Before reinstalling the blade, ensure it’s balanced and evenly sharpened on both sides. If not, even it out with more sharpening.

Reinstall the blade: With the blade facing the correct direction, reattach the blade using the nut or bolt you removed. Tighten it before flipping the mower back over and refill the gas tank if you’ll be using it again this season.


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