How to Replace a Lawn Mower Blade

Sharp lawn mower blades cut grass better than dull blades.

Cutting grass dulls the lawn mower blade, which then causes the blade to rip the grass and damage it rather than smoothly cut the grass. Many homeowners choose to remove the lawn mower blade, clean and sharpen it before reinstalling the blade. After repeated honing, sharpening a lawn mower blade is no longer possible and requires blade replacement. Running an object over with the lawn mower can irreparably damage the blade and make lawn mower blade replacement necessary.

Things You'll Need

• 2 bulb siphons
• Portable gas tank
• Container
• Broom
• Garden hose
• Wood, large rock or patio paver
• Socket
• Ratchet

Instructions

1. Locate the spark plug on the lawn mower's engine. Remove the spark plug or the spark plug wire to prevent unintentionally starting the lawn mower.

2. Siphon the gas out of the lawn mower's gas tank into a portable gas tank with a hand-powered bulb siphon. Siphon the oil out of the lawn mower into a container with a second bulb siphon to avoid mixing gas and oil.

3. Tip the lawn mower sideways or to the back to gain access to the mower blade.

4. Clean stuck-on grass off the blade and underside of the lawn mower with a stiff broom or spray a forceful stream of water at the blade and underside of the mower with a garden hose.

5. Block the blade's rotation by wedging a piece of wood, large rock or patio paver between the blade and lawn mower housing.

6. Fit an appropriate size socket over the nut or bolt holding the blade in place. Attach a ratchet to the socket and turn the ratchet handle to the left to loosen and remove the nut. If the nut or bolt remains stuck, spray it with penetrating oil and wait five to 10 minutes before removing the nut or bolt.

7. Pull the lawn mower blade off the underside of the lawn mower.

8. Place a new lawn mower blade back in its position. Make sure the blade fits onto the underside the same way as the removed blade. Put the nut or bolt back in place. Turn the nut or bolt to the right by hand until the nut or bolt is snugly in place. Fit the socket over the nut or bolt and turn the ratchet handle to the right to tighten the nut or bolt the rest of the way.

9. Set the lawn mower upright on the ground. Fill the gas tank and replace the oil. Put the spark plug or spark plug wire back in position.

Tips & Warnings

• Replace the blade with the lawn mower manufacturer's recommended blade.

• Wear gloves when replacing a lawn mower blade.

• Do not siphon gas near an open flame.

• Do not use a power siphon or shop vacuum to remove gas or oil from a lawn mower.

• Avoid using an adjustable wrench, as the wrench has a tendency to round off the edges of nuts and bolts.

• Only remove and replace lawn mower blades once the lawn mower is cool enough to touch comfortably.

References

• "New Fix-It-Yourself Manual: How to Repair, Clean, and Maintain Anything and Everything in and Around Your Home"; Reader's Digest Editors; 1996