Instructables
Picture of Sharpening a Lawn Mower Blade
This instructable will lead you step by step to sharpen a lawn mower blade. It is important to keep your blade sharp, for it decreases the time spent mowing as well as helps with overall lawn care. A dull blade will rip the tops off your grass, leaving it vulnerable to disease, while a sharp blade provides a clean cut that helps the plant recover quickly. Depending on the tools you use and how bad the blade is, this can be done in anywhere from 15 to 40 minutes. Sharpening is a simple task, even for a novice. It may take a few times to master however. Yet by doing this by yourself, you will reduce the time to cut your yard, while providing a better cut, as well as keeping your total maintenance cost down.

Step 1: Gather Materials

Picture of Gather Materials
These are some materials you may need for this project. Because there are various ways to accomplish this project with different tools read carefully.
• Clamp  (If using a grinder this may not be needed.)
     Table Clamp OR C-Clamp
• Safety Glasses (Really only necessary if using grinder.)
• Ratchet (Or some kind of wrench)
• Screwdriver (Or something to clean the blade.)
• Bolt & Nut (Optional)
• Leather Gloves
• Block of Wood
• File
• Grinder
The file and grinder are not both required. Can be done with one or the other, or both.


Step 2: Get to the Blade

The first step to gain access to the mower's blade.

1. Remove or disconnect the spark plug.
Warning: There is a chance the motor is at the top of its compression stroke and with a little bump could turn over causing the blade to spin under power.

2. Locate the carburetor
The throttle cables run to it. Another reference may be the primer, or little bulb, that you push before you start your mower.


3. Turn the mower on its side with the carburetor up.
Caution: Gas cap could have an air hole in it so you may leak gas.

 
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MPLangan3 years ago
In my experience (I am only 22 but have been mowing lawns for 16 years) you should never sharpen your blade.
Lawn mowers are made to work just like strimmers, using the high speed, they swosh the grass of, if you know what I mean.
My sharpening the blade your are just going to make the blade not last very long, and make it get more nicks in it. The ideal, is a nice rounded edge.

But that's just my 2 cents.
This is about as wrong as wrong can be.
You MUST be kidding, MPLangan. Blades must be kept sharp to do a decent mowing job. Nice Instructable Coder08. Thanks for including all the necessary safety tips. A lot of bad things can happen when changing or sharpening a blade. My neighbor cut his hand installing newly sharpened blade & got 12 stitches at the emergency room to close the cut at the base of his thumb. Leather gloves or blade clamp would have prevented it.
coder08 (author)  MPLangan3 years ago
For proper maintenance of your lawn, a sharp blade is required.A dull blade does not cut the grass, but rather rips the grass. By not providing a clean cut, your lawn is more open to disease, which can lead to a brown yard. A clean cut allows the grass to heal properly, while leaving your lawn looking much nicer.
The design of the blade is directly related to how a lawn mower operates however. A mulching mower has a different blade than a mower that throws the grass into a bag; however they both have a specific bend that causes lift at high speeds, in order to draw the grass up toward the blade. These bends are on the back of the blade.
Now if you sharpen the blade incorrectly, you can decrease the life of the blade. However, the initial cutting edge of a blade, when brand new, is the ideal edge. Research has been done that proves that angle provides the best cut to edge retention. Therefore if you sharpen your blade to look like a razor blade, you will get a very nice cut, but the edge will wear quickly, and is much more likely to get nicks in it. While if you go to a more vertical edge it will keep its shape better but not provide as well of a cut.
So it is good to sharpen your blade as long as it is done properly.
Beemer103 years ago
I must disagree. Look at the resulting cut from a "nice rounded edge".
The grass is shredded rather than cut cleanly, resulting in bruising and die-back. I'll take a sharp blade any time for lawn grass. If you are just cleaning up a rough area, it probably doesn't matter, but a sharp blade puts less load on the motor.
Just my 2-cents worth.
CapnChkn3 years ago
4 words.

Rub Ber Mal let.

And don't hit the drive with anything, you'll just break it. Get one of those fancy Crescent wrenches.
Topcat20213 years ago
Good set of instructions you have made for changing the blade on a lawn mower, I do the same thing but I also change the oil and clean out the fuel tank and change the air filter when doing a blade sharpening (makes for less mess and the whole mower gets serviced in the process.)
Again great job on the documentation
Dan