Riding mower blades over time become dull, nicked, or bent. When this is the case, the lawnmower blade becomes ineffective, and instead of cutting the grass, it tears the grass. Sometimes, if the blade is in bad enough shape, it will tear out the grass altogether. This kind of damage will subject your lawn to brown edged grass and the destruction of turf and can expose the grass to rot and disease. Sharpening your lawn tractor blades periodically will alleviate the potential problems that dull blades can cause, and will make the process smoother overall. It will also maximize the performance of your lawn mower to ensure proper operation and a long life.
Step 1 - Remove the Deck on the Mower
Remove the cutting deck from your riding lawnmower so that you can get to the blades. How you remove the deck will depend on the type and style of mower that you own. If in doubt, check the manual.
Step 2 - Remove the Blade from the Deck
Flip the riding mower deck (which houses the cutting blades) over so that you can get to the blades. Most are simply secured with a large nut in the center. Put a chunk of wood in between the side wall of the deck and the blade to stop the blade from turning as it is removed. Use the sockets to loosen the nut. Once the nut is off, lift the blade straight up to remove it.
Step 3 - Examine the Blades
Examine the blade to ensure that it isn't bent. If the blade is bent, you should not try to repair, sharpen, or reuse it. Once it is bent, it is scrap. If the blade is used while bent or out of balance, this will throw off the continuity of the rotation of the blade, hence throwing the entire cutting mechanism out of line. This can result in increased vibration in your machine and can ultimately ruin your mower.
Step 4 - Sharpen the Blades
Secure the blade to a sturdy workbench with C clamps or a vise. You can use an angle grinder to remove any large nicks or divots in the metal, but be careful not to grind the metal down too much. You should ultimately put the edge on by hand. Using a large utility file, run the file in long, even strokes down the edge of the blade. Count your strokes, ensuring that you give an equal number of strokes to each side.
Step 5 - Check the Balance
You will need to check the balance of the blade to ensure that one side is not heavier than the other. If the blade is out of balance, this can damage your mower. You can set the blade on a dowel or the handle of a screwdriver. If it leans to one side, do a few more strokes to the heavier side, checking the balance frequently, to bring it back into balance.