How to Change A Lawnmower Blade

By Robert Robillard on How To

Changing a Lawnmower

Sharpening your lawn mower blade is an easy do-it-yourself project.  I sharpen my blade at the beginning of Spring and again mid-summer.  Often times if my son hits a rock I have to sharpen it sooner.

A good way to tell if your blade is no longer sharp is to take a look at the grass after you have mowed it. If the tops of the grass blades are ragged, uneven or torn, then your blade is dull. If the grass has a nice clean cut, you don’t need to sharpen it yet.

Removing the blade to sharpen it can easily be accomplished with the steps outlined below.

How to Change A Lawnmower Blade

1.  Turn off the mower and unplug the spark plug wire.  

2.  Tilt the more on its side, gas tank down to keep gas from leaking into the motor or muffler area.

Gas does leak out so do this in an area where the gas will not cause damage.   Sometime I unscrew the gas cap and put a piece of saran wrap over the gas tank opening and then apply the cap over the saran wrap.  This keeps the gas from leaking out.

Another method is to siphon all the gas from the gas tank before turning unit over.

3.  Remove any debris from the lawnmower deck area. Brush away any grass clippings, twigs or obstructions from the drive belts and deck top.

4. Place a block of scrap wood between the mowing deck and the tip of the lawnmower blade. This will stop the blade from turning when removing the bolt or nut.

5.  Use the correct size socket or wrench to loosen the blade retaining bolt. Slowly and carefully remove the blade from the spindle

6.  Use a grinding stone to get a “rough” edge on the blade.  If you do not have a grinder, you can do the entire procedure with a mill file.

7.  Fine tune the blades edge with a mill  file.  I use a diagonal, forward and back motion with the file to get a super sharp edge.  Try to remove equal amounts of metal from both sides of the blade.

8.  Install the sharp blade over the spindle and return the bolt to the spindle screw. Tighten the bolt or nut to specified torque requirements in the owner’s manual of the lawnmower.

9.  Place the mower upright, remove anything blocking the gas cap and attach the spark plug wire.

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About the author

Robert Robillard

Carpenter / Remodeler / Editor

Rob Robillard is “The Concord Carpenter” Rob is a builder, general contractor, carpenter, woodworker, and editor of Concord Carpenter and ToolBoxBuzz As a General Contractor and carpenter, Rob owns and operates Concord Carpenter LLC. A full-service remodeling and construction company. Rob is a recognized leader in home building best practices and a source for how-to information for building professionals. On this website, Rob covers all aspects of home construction, building science, home improvement, woodworking, remodeling, and some of the best product and tool reviews. Rob is in charge of our Tool and Product Review series - Concord Carpenter Videos where we post all of our tool reviews and video tutorials. Rob approaches remodeling and building construction with a pragmatic and problem-solving approach. He enjoys using his knowledge and experience to help and educate building professionals as well as DIYers on best practices in the construction and remodeling industry. He's a strong advocate for "raising the bar" in the construction trades and promoting the trades to youth. #BeAMentor #Green2Great Craftsmanship, quality, and pride guide his journey on this channel The Concord Carpenter's motto: "Well done is better than well said!" : Read more about Rob

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