Mulching blades cut grass in a much different way than regular lawn mower blades. Regular lawn mower blades cut the grass blades once and then shoot them out a side chute onto your lawn. The clippings can look unsightly when slowly decomposing on top of your lawn. A mulching blade cuts the grass blades many times before dispersing them directly into the lawn below the mower. The clippings are very fine and decompose rapidly out of sight. Mulching blades may need to be replaced from time to time, especially if they are severely nicked or gouged.
Drain the gas from the tank of your lawn mower with a siphon hose and gas can. Use a siphon hose with a priming bulb for easy priming. Pull the spark plug wire off of the spark plug.
Lift the lawn mower up and lay it down on its side. Slide the correct size wrench onto the bolt that connects the mulching blade to the lawn mower. It will be located in the middle of the blade.
Wedge a board between the mulching blade and the housing of the lawn mower. This will prevent the blade from turning when you turn the bolt.
Turn the bolt counterclockwise with firm pressure. Unscrew it completely and remove both the bolt and the lawn mower blade. Retain any washers that come off with the bolt so you can reinstall them with the new blade.
Position the new mulching blade into place. Ensure it is in the same orientation on the lawn mower as the old blade. Put the washers into place and screw the bolt on. Tighten with your box wrench.
Set the lawn mower back down on all four wheels and fill the gas tank back up. You are now ready to cut grass again.