Not A Bench Grinder: How To Sharpen Lawn Mower Blades Quickly & Efficiently

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Mowing the lawn is an essential task — unless you want to live in an overgrown jungle, that is. And while mowing a lawn isn't in itself difficult, you do need to take steps to ensure that your lawn mower stays in good condition to allow for proper cutting. A sharp mower blade is key, and you can actually sharpen it yourself at home using a tool from your workshop: a belt sander, which isn't just used in wood applications, but in metal, too.

Because a belt sander is used to remove material, it makes sense to use it to sharpen a blade, as you're basically removing metal to create a sharper edge. As for why your mower needs this regular upkeep, it's because only a sharp blade can ensure grass is cut cleanly and evenly, which in turn, keeps your lawn healthy. (Here's how to know it's time to sharpen your lawn mower blades.)

You could take your blade to a professional, where costs begin at around $30 on average. Or, as said, you could sharpen it with a belt sander at home. If you don't already have one, you could get a stationary belt sander in the $100 to $200 range. It's a specialized tool, though, so that's another consideration in going this DIY route. Remember, you should sharpen a blade once every 20 to 25 hours of cumulative use.

Make sure you use personal protective equipment, specifically eye and ear protection and safety gloves. Next, you'll need to ensure that you've disconnected your mower from any power, which for gas mowers means disconnecting the ignition wire from the spark plug. Electric mowers should have their batteries taken out. Next, remove your mower blade, and clean it of any grass and/or grub.

Your stationary belt sander needs to be firmly secured in place to safely sharpen. For the belt, use a 60-grit or 80-grit. Make sure your belt is grinding away from the cutting edge and grip the mower blade with both hands.

Once you've lined up the angle of the mower blade with the sanding belt, you will want to keep the blade moving across the belt with a light touch until it starts to sharpen. This is not a job that can be rushed (and it also doesn't take very long). You'll need to do this on both sides of the blade, making sure that they're equally balanced and sharpened so that the blade is level when it's put back on the mower. Use a blade balancer, like this one from Oregon ($8.48), to check.

Note that as the blade is sharpened, it will heat up. Noticeable darkening of the lawn mower blade (black or blue, per Empire Abrasives), will indicate that it's getting hot, at which point you should dip it in water (like in a bucket). (See what common mistakes everyone makes when sharpening lawn mower blades.)