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How to Sharpen A Lawn Mower Blade Using a Grinder (Example: Craftsman Mower Blade)

Posted By Ethan On August 4, 2008 @ 7:30 am In Lawn,Project Guides | 11 Comments

Performing mower maintenance at least once every 12 months is essential to keeping your lawnmower in top running condition.  This article is the third in a series of lawnmower maintenance articles that cover complete lawnmower care

We’re performing maintenance on both a Craftsman 6.5 horsepower (HP) self-propelled mower, and a lighter duty 4.5 HP Murray mower.  Both push mowers are powered by Briggs & Stratton 4-cycle engines.  For this article, we’re only going to show the sharpening process on the Craftsman, but the principals can be applied to all mower blades.

Properly maintaining your lawn mower blade is important. A sharp blade ensures that grass is cut (rather than torn) evenly and on the first pass, and the engine won’t have to work as hard.

Underside of mower, removing blade [1]

Remove the Mower Blade

Step 1: Disconnect the spark plug to keep the mower from accidentally starting. The spark plug is connected to a wire and is usually located on the front of the engine.  Simply pull the wire off the spark plug to disconnect it.

Step 2: Tip the mower on its side. It’s best to have an empty gas tank but not necessary (in my opinion). Tip the mower keeping the air filter up to avoid oil seeping into the air filter compartment.

Step 3: The blade will be secured by a nut (typically standard thread). Turn it counter-clockwise to loosen. Some mowers will have overlapping holes used to lock the blade in place. Find something like an old screwdriver and insert it into both holes. The nut will be very tight so be prepared to use a little elbow grease.

Dull mower blade [2]How to Sharpen the Blade

I used a hand-held grinder but the basic principals can be applied to a bench grinder too.

Step 4: Inspect the blade. If the blade has too many dings, it may be time to replace it. Notice that the sharp edge is created by angling only one side of the metal. This is the side to work on. Don’t grind the other side

Step 5: Secure the blade with some kind of vise or clamp. Be aware of your surroundings as lots of sparks will occur when you start sharpening. This step is best performed outside. Be particularly aware of any sawdust or combustible materials that may be in the line of the sparks, as these could ignite.

Step 6: Run the grinder along the blade with smooth even movements. Make sure the grinder is spinning toward the cutting edge. Follow the manufacturer’s bevel as best you can.

sharpening a mower blade [3]Balancing the Blade

The end result should be a balanced blade. If not, the blade will not cut evenly, and the mower will vibrate which can damage the mower engine.

Step 7: To check the balance, partially drive a nail straight into a stud. Hang the blade on the nail to see if one side dips lower than the other, and grind the heavy side until the blade is balanced.

Step 8: Re-install the blade on the mower ensuring that all washers and nuts are installed in the same order they were removed, and that the final nut is tightened.  Start the engine.  If the mower runs smooth, you’re done.  If the mower shakes or vibrates, either the blade is unbalanced (see Step 7) or it has not been installed properly.  Track back through these steps to ensure you did everything right.

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Check back as One Project Closer will have more DIY maintenance posts to come.

What do you think? When was the last time you checked your mower blade?


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