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Just like any other outdoor equipment, a lawn mower needs regular maintenance to work properly, even if you have one of the best lawn mower models. The blades must be sharp enough to cut grass cleanly, but sharper doesn’t automatically mean better. You’ll need to find a good balance, but you don’t need to sharpen lawn mower blades to a razor edge.
The reason you don’t want a razor-sharp edge is that the blades will chip. That kind of edge tends to fold over, which can notch and dent the blade, especially if it hits dirt or tiny rocks. This can also lead to dull blades and repeated sharpening, eventually shortening their life. As such, it will be prudent to learn how to optimally and safely sharpen your lawn mower blades. Though the blades should be sharp, it ought to be safe to touch the blade with your hand without risk of being cut; about a thickness of 0.030 to 0.045 inches.
When you sharpen, make sure you use hand and eye protection. Also, disconnect the power to the mower — unplug it or remove the battery to prevent any accidental starts. Additionally, remove and clean the blades first to remove any debris.
What does a properly sharpened lawn mower blade look like?
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Once removed, get a vise to lock the mower blade tightly for safety. Try not to overdo it so you don’t bend the blade. Then, take a hand file and slide it along the existing slanted edge of the blade, matching the original angle. Push the file forward in careful, long strokes using steady pressure, and keep doing this until the blade is sharp and smooth all the way across. Remember to always lift the file off the metal when pulling it back so you don’t dull the edge.
You could also use a power drill to sharpen the lawn mower blade. Again, use the vise, match the angle of the blade, and turn on the drill. Similar to using the file, grind the edge and make steady back-and-forth movements.
Regardless of the method, once you finish sharpening, place the center of the blade onto a mower blade balancer. If one side tilts downward, that end is heavier, so you’ll need to file or grind off a bit more metal from that side’s edge. Otherwise, if it stays completely flat and level, it’s balanced and ready to go. While there are different lawn mower blade types available, you’ll know you’ve sharpened a blade correctly when there’s a smooth, even slope all the way across, without any dents, scratches, chips, or similar irregularities.