Lawn mowers require regular maintenance to ensure that they cut the grass properly. The most important part of maintenance beside keeping the engine running is ensuring that the lawn mower blade is sharp and balanced. A sharp blade makes an even cut every time. Removing the blade before the mowing season and inspecting it for large dents, dull points and balance ensures the grass is being cut and not ripped. Keeping the blade sharp and balanced also reduces wear on the engine.
Put on gloves and safety goggles before working on the mower.
Disconnect the spark plug of the mower and remove all gasoline and oil from the engine. Roll the mower onto a tarp and flip it onto its side, so that the gas tank and oil crank case are under the carburetor, to prevent leaking.
Place a wood block at the bottom of the mower deck and secure the blade against it. Use a crescent wrench to remove the nut that holds the blade in place. If stuck, get the nut moving by hitting the crescent wrench lightly with a rubber mallet.
Inspect the blade to make sure it does not have any major nicks or bent areas, according to BobVila.com. Sharpen the blade if it is dull but free of major dents or nicks. Replace the blade if sharpening is not possible.
Set the bench grinder so the rest is at the same angle as the blade of the mower. This helps guide the blade along the grinder, according to BobVila.com.
Turn on the grinder and find an area of the blade that is dull with the angle still visible. Grind the blade slowly by sliding it along the grinder in one direction, moving the entire length of the blade down the grinder to keep it even. Make several passes.
Balance the blade on an angle iron, with the iron under the center of the blade to ensure it is balanced. Do this every few passes along the grinder. Clean the underside of the mower and replace the blade once sharpened.