How to Fix a Broken Lawn Mower Blade

sharpening a damaged lawnmower blade
  • 2-3 hours
  • Intermediate
  • 0-100
What You'll Need
Metal file or sharpening wheel
Gas container
Adjustable wrench

Rocks, metal and other debris that are harder than the steel blade of a lawn mower can find their way onto your lawn. When the blade finds this debris, it may become chipped, bent or even broken. When this happens, you can replace the lawn mower blade or fix it. Here are some steps that will help you repair it.

Step 1 - Decide Whether to Repair Your Broken Mower Blade

You can usually tell your lawn mower blade is damaged or dull, even without looking at it. A blade with nicks, dents or missing chunks will usually cause the mower to vibrate or shudder when running. A bent blade will almost always produce uneven streaks and edges on your mowed lawn.

Step 2 - Prepare your Lawn Mower to Remove Its Blade

Although you could work on the blade while it is attached to your mower, you will find this method both difficult and time consuming. The best you could do without removing the blade would be to try sharpening the blade with a metal file.

But since this method would be awkward and would likely take more time than removing the blade, you should take the blade off the mower to work on it.

damaged lawn mower blade with tools on a lawn

Step 3 - Turn Your Lawn Mower Over

Before you upend the lawn mower, you'll need to drain its gas and oil. A hot engine can ignite gas or gas fumes that come into contact with it. When the engine is cool, remove the gas tank cap and turn the lawn mower on its side so the gas drains into a container you have placed beneath it.

If the gas and container are clean, you can use a funnel to pour the gas back into the lawn mower when you're through repairing the blade. Drain the oil in the same way.

Step 4 - Remove the Blade

With the gas and oil drained, turn your lawn mower over so the blade is exposed and easy for you to reach. Use a wrench to loosen and remove the nut that holds the blade in place. If you plan to hold the blade with your hand, be sure you are wearing gloves.

Step 5 - Sharpen the Blade

If the blade is only dull (but not bent or chipped), you will be able to sharpen it with a metal file, grindstone or emery wheel. If the blade is bent or has large chunks broken out of it, you should replace it with a new one.

Step 6 - Finish

Reattach the blade to the lawn mower. Take care to tighten the nut that holds the blade in place. Turn your mower upright, replace the gas and oil and give it a test run.