

How to Change the Blade on a Walk-Behind Lawn Mower

Length of Clip:  02:56

Check out these tips for sharpening and replacing lawn mower blades


To properly maintain your lawn mower blade, you should check it at least once a season, and any time you strike an object.  If you strike an object and your mower seems to vibrate excessively, you must have it checked out by a servicing dealer for a bent crankshaft or other damage.


One way to tell if you need a replacement lawn mower blades is to pay attention to the tips of your grass.  If it's turning brown between mowing, it is a sign that your blade may be dull.  Damaged grass needs more watering and is more susceptible to disease. Replacing or sharpening your blade can help you maintain a lush, healthy lawn.  You can use a lawn mower blade sharpener to sharpen blades, but a blade should be replaced if it's chipped, bent or too worn to be sharpened.  make sure any replacement lawn mower blades meet all OEM specifications.

Step 1: Prepare your mower for blade removal

Because you'll need to turn the machine on its side to change the lawn mower blade, it is important to protect against spilled oil and fuel. Running the mower until it's out of gas will help avoid a spill, but you can also drain the fuel tank using the Arnold Siphon Pump. To avoid burns, use caution when working around a hot engine.  If time allows, let the engine cool down before you change the blade.  Important: Remove the spark plug wire to assure the mower won't accidentally start.

Step 2: Check the lawn mower blade

Tip the mower on its side with the engine air filter facing up. This will keep engine oil from getting into the carburetor and air filter. Inspect the blade for wear or damage. You should check your cutting blade at least once a season to make sure it's sharp. A dull blade will tear rather than cut the grass, and can turn grass tips brown, making your lawn not look its best. Also be sure to check the blade for damage any time you strike an object. If you hit something and your mower vibrates excessively afterward, have a servicing dealer check it for a bent crankshaft or other damage.

Step 3: Prepare to remove the blade

If you decide to replace the old blade, you may want to wear gloves to protect your hands from any sharp edges. Use the Arnold Blade Removal Tool to hold the blade in place. The Arnold blade removal tool can be purchased on this website and where mower parts are sold.

Step 4: Remove the lawn mower blade

Using the proper size socket, loosen the bolt securing the cutting blade to the engine drive shaft. Some units may have two additional bolts securing the blade adaptor to the blade. Loosening them before you remove the blade from the unit will make your job easier. Before the blade is removed, make note of the orientation of the blade. You'll want to assure that the replacement blade is oriented the same way, with the fins pointed up. Remove the blade from the mower and keep the blade adaptor parts for installation of the new blade.

Step 5: Use a lawn mower blade sharpener for blades in otherwise good condition

If you simply need to sharpen your blade, instead of replacing it, you can use the Arnold Blade Sharpener and Balancer, which can be purchased from this website, or where mower parts are sold.

Step 6: Install the replacement lawn mower blade

Assemble the new blade and blade adaptor on the engine crankshaft. Tighten the blade bolt to the proper torque setting as indicated in your operator's manual.

Step 7: Right the mower and you're good to go!

Remove the blade removal tool and return the mower to the upright position. Reconnect the spark plug wire and you're good to go!

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