How to Sharpen a Mower Blade

A sharp blade cuts grass properly.

A sharp lawnmower blade is essential for keeping your lawn healthy and looking its best. A dull blade can tear the grass blades, leaving them susceptible to browning and diseases. Sharpen your power mower blade at least once a year, usually before the mowing season begins. You can sharpen the blade with a simple hand tool. Before you get started, though, drain the gasoline out of your lawnmower's tank and into an approved fuel container.

Things You'll Need

• Wrench or socket
• Block of wood
• Bench vise
• Coarse-grit metal file

Instructions

1. Disconnect the lawnmower's spark plug. Turn the mower on its side. Place a block of wood between the mower deck and the blade to hold the blade in position. Loosen the blade's center bolt with the appropriately sized wrench or socket. Remove the bolt, then the blade.

2. Put one end of the mower blade into your bench vise and secure it in place. Run your coarse-grit metal file from the inside toward the edge of the blade, following the existing angle. Make individual strokes, rather than sawing back and forth -- the file only removes metal as you push it. Don't sharpen the flat edge, but you can smooth the slight ridge that forms as you sharpen, according to Mother Earth News.

3. Continue working the file across the blade until the edge is sharp all across. Remove the blade from the vise and flip it around. Secure it in the vise and sharpen the other side as you did the first.

4. Check the sharpened blade for balance -- if it's unbalanced, the blade won't mow properly. Place a wood dowel, a hacksaw blade or a long nail in your vise and tighten it. Slip the mower blade's bolt hole over the dowel, blade or nail. If it the blade falls to one side, it isn't balanced and needs more filing. Place the blade back in the vise and file the end of the side that is too heavy. Keep filing and checking for balance until the blade hangs evenly.

5. Reinstall the sharpened blade on your mower and tighten the bolt. Tip the mower upright and reconnect the spark-plug wire.

Tips & Warnings

• check your mower blade for balance prior to reinstalling

• use a medium file

• An unbalanced blade will wobble when the lawnmower is running.

References

• Mother Earth News: A Midsummer's Sharpening -- How to Sharpen Your Lawn Mower Blade