Sharpening your mower blade is not difficult. With a set of wrenches to remove the blade, a block of wood to stop it from spinning, a vice to hold the blade and a few standard files, you can easily do a quick sharpening to improve the performance of your lawn mower.
Removing the Blade
To sharpen a lawnmower blade, you will need to remove the blade from the mower. Some mowers use a single bolt to secure the blade; others use two bolts to secure the blade to a mounting plate. When removing the blade, wedge a block of wood between the blade and the mower deck to stop it from spinning.
Turning the Mower on its Side
To get at the mower blade for removal, turn the mower on its side with the carburetor facing up. If the carburetor faces down, it will likely leak gasoline on the floor or ground where you are working on the mower.
Mulching blades aren't straight. Because they are curved, they create a vacuum that holds grass in the blades for a longer period of time, thus allowing them to be chopped more finely. To sharpen a mulching blade, use a flat file on the flat parts of the blade and a round file on the curved cutting edge.
General Filing Tips
When sharpening your mower blade, count the number of strokes on one side before switching to the other side. Use the same number of strokes on both sides to keep from making one side heavier than the other. If one side is heavier, the blade balance will be off and could create a vibration in the mower.