Many people have never sharpened the blades of their lawn mower before. However, sharpening these blades will not only cut your lawn more evenly, it will save you power due to less resistance.
Some people say that you should sharpen your mower blades every couple of months. This all really depends on how large your yard is and how often you mow the lawn.
To remove the lawn mower blade or blades, first disconnect the battery and/or spark plug cable. This will prevent the mower from accidentally starting up while you are removing the blade.
Tip the mower over and make sure the blade will not move while you are trying to remove it. This can be done using a c-clamp, block of wood, or a blade holder. Be sure to wear safety gloves!
Make sure the nut and bolt attaching the blade to the mower are clean of debris. Remove the nut using a wrench or ratchet, and take off the blade. Be sure to reattach the nut so it does not get lost.
Now that the blade is free, clean off any debris with a putty knife or scraper. Be sure to examine the blade, making sure the blade does not have any bent places or considerable damage.
If the blade is damaged or bent, do not try to sharpen it. Damaged or bent blades will not cut your grass well, and bent blades can actually damage the interior of your mower and anyone nearby!
A new blade costs around $20 for most mowers. If you do not have the supplies or time to sharpen blade yourself, smaller hardware stores will sharpen them for about $10.
Some mowers come with their own sharpening kits, but those without kits typically use a bench grinder, blade grinder, or hand grinder for this job. Cheap blade sharpeners are available at hardware stores – some even attach to a power drill. Others prefer to use metal files; while this will take more time, it will get the job done.
Those with a hand-held grinder, sharpener, or file should clamp down the mower blade. This will keep the blade still while sharpening and frees up both hands for controlling the grinder.
Take a good look at the angle of the blade edge and make sure that it is not altered when sharpening. These angles were determined by the manufacturing company to ensure an accurate cut.
Altering angles can cause a lot of problems. Narrow angles will dull quickly or get more nicks. Before you know it, the blade will need sharpening again. Wide angles create a dull edge and will actually tear your grass instead of cutting it. Tearing grass will leave your lawn prone to disease and sickness.
While sharpening, try to grind the sides evenly. These blades are precisely balanced, and when that balance is altered, it can wobble and bend when in use. Those using files usually count the strokes made on each side of the blade to ensure it is even. Those with grinders should keep the grinder (or blade, for those with bench grinders) in constant motion.
Don’t forget safety gloves and glasses!
Once finished, you should be able to balance the center of the blade on your finger. Once the blade is sharpened, any jagged edges or burrs (small amounts of metal jutting out) can be removed using a metal file.
Attach the blade back onto the lawn mower, making sure the blade is facing the correct way. Reattach the spark plug wire or battery, and you are ready to mow that lawn!