How to Stop the Spindle From Moving When Taking Lawn Mower Blades Off

Disconnect the mower’s spark plug by pulling the rubber plug lead boot off the plug and securing it away from the plug terminal.

Remove the fuel tank filler cap and place a small square of heavy-duty plastic sheet over the filler spout, replace the cap and tighten it securely to prevent gasoline from spilling out of the vent hole when you tip the mower on its side.

Place a drop cloth on the ground in a well-ventilated area, move the mower onto the cloth and tip it on its side, placing the carburetor at facing upward.

Scrape off all compacted grass clippings from the underside of the mower housing with a plastic spatula. Wipe the inside surface of the housing clean with a damp cloth.

Place a special blade clamp over the blade and attach it to the rim on the underside of the mower as directed in the instructions that came with the clamp. Alternatively, wedge a short piece of 2-by-4 between the leading edge of the blade and the mower housing to prevent the blade from turning.

Remove the mower spindle bolt and washer by turning it counterclockwise with a socket wrench, then lift the dull blade off of the spindle.

Bolt a new blade, or a sharp, well-balanced used blade, onto the spindle. Hold the blade steady with one hand and tighten the spindle bolt with the socket wrench; the reaction from the clockwise spinning blade will tighten the bolt even further.

Tip the mower back onto its wheels, reconnect the spark plug and remove the square of plastic from under the filler cap.