How to Sharpen a Power Mower Blade

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A dull mower blade doesn't cut grass blades--it tears them, leaving the grass vulnerable to disease or damage from the sun. How often the mower blade needs sharpening depends on the size of your lawn and how often you mow, but plan on doing the job at least every four to six weeks.

Steps:
1. Drain the gas and disconnect the spark plug wire in your power mower so the motor doesn't turn over while you're working.

2. Tilt the mower on its side, and wedge a block of wood between the blade and the mower deck to keep the blade from turning. You can also buy a device called a Blade Buster that locks the blade in place while you work on the mower.

3. Use a scraper or putty knife to clean any built-up debris from the underside of the mower deck.

4. Using an adjustable wrench, remove the bolt from the center of the blade.

5. Pull off the blade and clamp it in a bench vise.

6. Check the blade edges for small nicks, and remove them using a flat medium file.

7. Sharpen the blade by moving the file toward the cutting edge with smooth, even strokes. Follow the original bevel of the blade as closely as you can.

8. Make the same number of strokes on each edge. If you take more metal off one side than the other, the blade will be out of balance. An out-of-balance blade cuts unevenly; it also makes the mower vibrate, which can cause serious damage to the engine.

9. Test the balance by resting the blade on a dowel or the handle of a screwdriver. If one side points up, sharpen the other until the blade lies flat. (Or use a blade balancer, available at garden centers and hardware stores.)