How to Sharpen Lawn Mower Blades

Sharp blades help keep grass green.

Mowing with a dull blade isn't just more difficult, it's damaging to your grass. A blade that is not sharp tears, rather than cuts grass, leaving the ends ragged and prone to disease. Get ahead of the game this mowing season by sharpening your lawn mower blades to do the job right the first time.

Things You'll Need

• Vise or clamp
• File
• Wrench
• Hammer
• Nail

Instructions

1. Disconnect the spark plugs on your mower to eliminate possible hazards. It does not matter if you own a walk-behind lawn mower, a ride on mower, or a commercial tractor, this is always necessary. Consult your owner's manual for the exact location if you can't find it.

2. Remove the blade from the bottom of the mower with a wrench. If you can't get it off the central bolt, due to years of use and rust, apply a lubricant, like WD-40, and try again.

3. Affix the blade to a workbench or other sturdy surface with a vise or clamp. Run a file or sharpening stone over the blade over the cutting edge of the blade in one direction only. Attempt to maintain the original angle of the cutting surface, about 40 degrees. A blade honed to a knife's edge is too weak to stand up to mowing, while a blunter blade does not cut cleanly.

4. Hammer a nail into a wall stud in your workshop or garage so it is perpendicular to the wall. Ensure that its head is narrow enough that the hole at the center of the blade can slip over it.

5. Put the blade over the nail and attempt to balance it horizontally. If it tips to one side, it is out of balance and you need to file more on the heavier side. A well-balanced blade produces fewer vibrations and less wear on your mower's engine, according to University of Florida Extension.

6. Replace your balanced, sharpened blade on the mower. Sharpen your blade every six months for best performance.

Tips & Warnings

• Check your grass after the first few cuts to make sure that the blade is cutting and not splitting the grass.

• If elbow grease is not one of your strong suits the there are grinder bits for sharpening steel that lock into the end of a drill.

• Never leave sharpened blades unattended.

References

• University of Florida Extension: Garden Solutions - Sharpening the Mower Blades
• University of Florida Extension: Mower Magic
• This Old House: How to Sharpen Lawn Mower Blades