How to Sharpen Lawn Mower Blades
Grass cut by a lawnmower with sharp blades has a smooth top edge. If the grass looks jagged, like it was ripped, then it was cut by a dull blade. If the blade is severely damaged with nicks and dings from hitting rocks, then you may want to consider replacing the blade. However, if it is only dull and needs sharpening, then it is possible to sharpen it without much hassle.
First: Practice safe habits
In order to avoid serious injury, make certain that the mower is not running. Then. find the spark plug and disconnect the wire. Taking these precautions, though they may seem obvious, is necessary to safely remove a lawnmower blade. Take no chances when you work with powered equipment.
Second: Remove and prep the blade
Turn the mower on its side and remove the nut that holds the blade onto the mower deck. Once the blade is free, use a steel brush to remove rust that may have accumulated from damp grass. You may use steel wool to remove the rust, but a brush is easier and more effective.
Third: Sharpen the blade
Gasoline mowers that have a single blade are the easiest type of blade to sharpen. Use a file to make a smooth edge on the blade. Just follow the angled edge on the blade to maintain the balance. Do not file one side more than the other, as this may cause the blade to turn unevenly.
Fourth: Clean up and reassemble the mower
While the mower is disassembled, remove any mud or old leaves from the underside. Then replace the blade with the nut that you removed, and you are ready to mow.