If a rock or large twig has ever hit your mower blade, you may face the problem of having a bent mower blade. If the mower blade gets bent, it will no longer spin correctly on the lawn mower. Letting a lawn mower run with a bent blade can severely damage the engine. The typical solution to this problem is to replace the blade with a new one from your local home improvement store. However, if you have the patience and lots of hands-on skill, it is possible to fix bent mower blades yourself.
Disconnect the spark plug and remove the lawn mower blade from the mower. It is attached to the mower with a single bolt.
Clean the mower blade. Use a wire brush wheel on a right angle grinder to remove all debris and impurities from the mower blade.
Clamp the unbent end of the mower blade with your vice grips and heat the bent end of the blade with a torch until it is cherry red.
Lay the bent portion on an anvil or steel plate and pound it with your hammer. Go slow and easy and keep working it until the bent portion is straight again. It will take some trial and error to get it near perfect.
Use your angle grinder with your wire brush wheel to scuff the whole blade up again. Heat it up with the torch one more time and allow it to air cool. This should relieve the stress in the blade from straightening it.
Sharpen the lawn mower blade on each side until it is perfectly balanced. To check for balance, position the blade on your finger where the center bolt hole is. It should not tip toward either side, but rather stay perfectly balanced and level.
Reinstall the blade on your lawn mower and enjoy your newly straightened, sharp lawn mower blade.