How To Safely Sharpen Your Lawn Mower Blades By Hand

We may receive a commission on purchases made from links.

If you notice your lawn looking ragged, rough, or uneven after mowing, you may take it as a sign it's time to replace your mower. However, it more likely means you simply need to sharpen your lawn mower blades. Those who have never taken on this task may assume you need a lot of time and equipment. Indeed, tools such as bench grinders are certainly effective, but there are also several other ways to sharpen mower blades. 

One of the simplest ways to do so is hand-sharpening them with a file, sandpaper, or an abrasive compound. While this method doesn't require any specialized equipment or skills, there are some steps you must take to safely sharpen your lawn mower blades by hand. This means ensuring the blade is in a secure position, wearing protective gear, and utilizing your tools properly.

Besides a rough cut, other signs you need to sharpen mower blades include a change in your lawn's color from green to yellow or brown, taking more effort and/or gas to mow your yard, or random spots that are scalped by your mower. Additionally, visually inspecting the blade can also reveal clues, such as nicks, dents, and rust. Without noticing any of these signs, it is generally recommended to sharpen mower blades roughly every 25 operating hours regardless of what type of mower you have. Even if your lawn doesn't require that much time for mowing during a season, it's also a good practice to sharpen blades at the beginning of each year. That means everyone who mows should be sharpening blades at least once per year. So, knowing how to sharpen your lawn mower blades safely is paramount.

When it comes to safely sharpening your lawn mower blades, the precautions start before the sharpening even begins. Although you can technically leave your blade on the mower in order to sharpen it, it's best to remove it for safety, efficiency, and effectiveness. However, before attempting to do so, unplug and/or remove batteries from electric mowers and disconnect the spark plug wire on gas mowers. Since push mowers should be tilted on their side, you can also drain the gasoline. On riding mowers, raise the mowing deck to its highest level and securely block the front tires on a mower ramp or lift.

Once the blade is easily accessible, mark the bottom of the blade with a permanent marker, and remove the nut holding the blade in place while wearing gloves and protective eyewear. If the bolt is being stubborn, spray it with a shot of lubricating oil and wedge a wood block between the blade and the mowing deck to hold it in place. After the blade is removed, clean it with a rag or stiff brush to eliminate any debris or grass clippings. 

From there, you'll need to secure the blade in a vise, such as the Yost LV-4 Homeowner's Vise. Then, begin sharpening the blade by pushing the file or abrasive pad along the edge at about a 45-degree angle. Each stroke should only be in one direction — away from you and along the blade edge. Make sure not to move the file back and forth along the edge. Once one side is done, remove the blade from the vise, turn it over, and repeat the process. After both sides are done, reattach the blade to the mower.