Removal of a lawn mower blade is necessary in several incidences: when the blade is dull, when it is bent, or when it has several large chips. A chipped or dull blade rips at the grass instead of cutting it, causing disease and wounds that do not heal. A bent blade may also cause damage on the underside of the mower.
Tipping the Mower
Tipping the mower is required to access the mower blade on push mower types. It is necessary to tip the mower in the correct direction as fuel will leak into the carburetor if done incorrectly. Tilt the mower onto its side so that the gas tank is below the carburetor. This prevent petrol from dripping down into the open carburetor. You may also remove all the gas and oil. Remove the spark plug before working on the mower to prevent it from starting.
Securing the Blade
The blade will easily slip during removal is not secured. Wedging a piece of two by four on the bottom of the mower will do. Place the two by four at the bottom of the mower and turn the blade so that it catches on the wood. Wear gloves while working on the blade to prevent cuts and abrasions.
Spray the topside of the mower blade with spray paint to indicate which side of the blade is up. This prevents you from putting the blade on backwards when replacing it. A second hand should hold the blade in place, with the wood holding the other end secure. The bolt in the middle of the blade is turned using a crescent wrench. Sometime the nut is stuck due to debris. A squirt with a loosening oil will remove debris. Use a rubber mallet to gently tap the crescent wrench around the bolt if it is still difficult to remove.