Changing a blade in a Snapper lawnmower is a bit different from other mowers. The Snapper may use air lifts that attach to the mower blade. The air lifts increase vacuum performance when using a bagger and even increase air flow when you cut damp grass or wet leaves. It is best to purchase replacement blades from a Snapper authorized dealer. Standard blades may not have the necessary mounting hole you will need if you use the air lift attachments.
Place your Snapper lawnmower on a flat surface. Pull off the spark plug wire from the spark plug with your fingers. Bend the wire so that it does not accidentally make contact with the spark plug while you work on the mower blade. Put on your leather work gloves before removing the blade.
Tilt the mower on its side with the air filter and carburetor pointing up to help prevent fuel spillage. Wedge a block of wood between the blade and the mower deck to help hold the blade still while you remove the mounting bolt.
Remove the center mounting bolt that secures the blade to the motor shaft with an appropriate size socket wrench. If you have one of the 21-inch special blades, you may have two retaining bolts. Pull off the flat washer and the cone washer. Pull the mower blade off the motor shaft.
Inspect the drive hub that sits between the bottom of the mower deck and the blade. If the hub appears to have damage, replace the hub when you replace the blade. If your blade uses air lifts, remove the bolts and nuts with a socket wrench and pull the air lifts off the blade.
Take the blade to a Snapper dealer or home improvement center. Compare the new blade to the old one. Ensure that you get the blade that has the holes for the air lifts if necessary.
Install the air lifts to the new blade, if applicable. Place the air lifts on the blade and secure them with the retaining bolts and nuts. Place the blade on the motor shaft with the wording on the blade pointing away from the mower deck. Ensure that the drive hub fits between the upturned portion of the mower blade.
Place the cone washer over the motor shaft with the concave portion pointing toward the blade. Place the flat washer over the cone washer, if applicable. Thread the center mounting bolt into the motor shaft and tighten with a socket wrench.
Place the mower back on its wheels and plug the spark plug wire boot back on the spark plug.