Different lawn mowers have different-sized blades. Mowers with narrow decks have small blades, while mowers with wide mower decks have large blades. The common denominator with all types of lawn mower blades is that they are all connected to the engine shaft with a single bolt. The blade rapidly rotates around this axis and this is how your grass is cut. Large lawn mower blades can be easily removed from your lawn mower with a few tools.
Run the engine of the lawn mower until it is out of gas and take it to a smooth surface that is well-lit.
Grasp the sparkplug wire connector and pull it off the sparkplug. This will keep the engine from starting up while you are working on it.
Lay the lawn mower down on its side and locate the bolt that holds the lawn mower blade to the engine shaft. It will be in the center of the blade.
Take a length of 2-by-4 board and wedge it between the mower deck housing and the blade.
Adjust your adjustable wrench and slide it on to the bolt. Turn the wrench counterclockwise to loosen the bolt. Keep turning until the bolt can be turned all the way out by hand.
Remove the bolt along with any associated washers and set them aside. Grasp the blade and gently pull it off.