How to Easily Sharpen Your Lawn Mower Blade

A sharp mower blade keeps your lawn healthy.

Keeping your lawn mower's blade sharp will keep your lawn healthy and extend the life of the blade. A dull blade leaves ragged edges, making the blades of grass more susceptible to disease, pest infestation and browning, according to the Washington State University Extension. Your mower blade should be sharpened at least once a year. You can take it to a mower-repair shop or learn how to sharpen the blade yourself with some basic workshop tools.

Things You'll Need

• Work gloves
• Wrench or socket
• Metal file
• Bench grinder
• Safety glasses
• Lawn mower blade balancer

Instructions

1. Disconnect the mower's spark plug wire so the engine won't start while you work on the blade. Put on work gloves. Loosen the gas-tank hose from the engine. Place the end of the hose into a gasoline-approved container that's large enough to hold the fuel in the tank.

2. Turn the mower on its side. Hold the blade in place with a wood block. Unfasten the bolt that secures the blade, using the correctly sized wrench or socket. Turn the bolt counterclockwise to remove it, then set it aside.

3. Secure the mower blade in a vise on your workbench. Sharpen the blade by running a metal file on its beveled edge, following the angle created at the factory. If the blade needs a more serious sharpening, continue to Step 4.

4. Turn on your bench grinder. Position the mower blade so it's perpendicular to the grinder wheel. Pass the blade back and forth on the wheel to remove nicks.

5. Turn the blade at an angle and run it back and forth across the grinder wheel to sharpen the cutting edges. Grind all the way across each bevel, checking your progress frequently. You will see a shiny silver bevel in the locations that you have sharpened. Grind the bevel until it is sharp. Slide a piece of paper across the blade to test for sharpness.

6. Test the balance of the newly sharpened blade. Place it on a plastic lawn mower blade balancer; if the blade tips down on one side, it's not balanced. File or grind off metal on the heavier side until the blade is balanced. Don't take metal off the cutting edge.

7. Reinstall the blade, making sure it's facing the same direction as when you removed it. Line up the shaft bolt hole and the two alignment pins. Hold the blade in place, insert the bolt and tighten it by turning it clockwise.

Tips & Warnings

• You can work more safety if you use a longer wrench to remove the blade bolt.

• You can buy an inexpensive blade balancer at lawn-supply or hardware stores.

• Sharp or dull lawn mower blades can cut you. Use all precautions possible to avoid injury.

References

• WSU Clark County Extension: Grasscylcing
• This Old House: How to Sharpen Lawn Mower Blades