Lawn mower blades will eventually need replacing on a Toro lawn mower due to cracks, chips or the blades wearing out. Blades may require sharpening to cut well, but eventually will not hold a sharp edge due to age and use. Changing a lawn mower blade requires a minimal amount of time and tools. Having a second person to hold the lawn mower in position ensures that it will not fall and cause injuries.
Tip a push lawnmower backwards so that the front wheels are off the ground. Support the lawn mower in this position by placing the handle underneath a table, workbench or truck bumper or have a second person hold the lawn mower for you. For a riding mower, place wooden blocks or bricks behind the rear tires so that it will not roll. Place a hydraulic jack under the front bumper and raise it until the front is at a 45-degree angle to the ground. An alternate method requires removal of the riding lawn mower deck by placing a block under the deck on each side, lowering it entirely, removing the drive belt and removing the four nuts and bolts that hold it onto the deck.
Disconnect the spark plug wire to avoid any accidental starts or shocks. Pull the wire straight up from the spark plug to disconnect it. Put work gloves on to protect your hands from accidental slips while handling the old and new Toro lawn mower blades.
Unscrew the bolt from the bottom center of the blade by turning counter-clockwise with an adjustable wrench. Place either a block of wood or a large brick in front of one blade to wedge it in place so that it does not turn. If the bolt is stuck due to oil and grass build up, spray with a penetrating oil and use a breaker bar or pipe on the end of the wrench for extra leverage. Remove the bolt and set it aside. Remove the washers and set them aside. Remove the old blade carefully by pulling it straight down with medium force.
Spray the bolt that the blade rests on with a spray lubricant to clean its surface thoroughly. This maintenance will keep the new blade from binding and provide a clean lubricated surface for the new blade.
Place the new blade in position, making sure that the cutting side faces to the front of the mower and the edges that curve face the back of the lawn mower. Replace the washers, bolt, and tighten with an adjustable wrench. Pull the lawn mower handle out from under the table and set it on all four wheels or lower the jack with a riding lawn mower. If your Toro blade installation includes deck removal on a riding lawn mower, replace the deck in the reverse order of removal. Reconnect the spark plug wire.