6 Best Tools To Sharpen Lawn Mower Blades That Aren’t A Bench Grinder

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If you want your freshly mowed lawn to have that pristine look you find on golf courses and sports fields, you need a sharp blade that cuts grass cleanly rather than yanking and pulling it. A sharp blade is also good for the mower, which doesn’t have to work as hard to do its job when the blade isn’t fighting with the grass. You might think that replacing the blade is the safest way to ensure you have a sharp one, but that’s an unnecessary waste, especially if you have a large lawn or you mow frequently. Sharpening a blade is easy, it doesn’t take much time, and you don’t have to have a bench grinder to do it.

Sure, a bench grinder makes the job easier, but it can be expensive — especially a good one — and you also need a workbench on which to mount it. Some tools that aren’t as expensive call for a vise to hold the blade, and for that you also need a bench, but some tools can sharpen a blade while it’s still on the mower. They allow you to hone the blade frequently to maintain a sharp edge, removing it from the mower only when it needs rebalancing or you have to do some serious grinding to erase nicks and dents. A lawn mower blade doesn’t need to be razor sharp. The usual phrase pros use is “butter knife sharp,” and all these tools will easily achieve that.

This is the old-school blade sharpening tool, and for some, it’s still the best. The type of file you need is a 10- to 12-inch flat file with medium coarse teeth. You need a vise to hold the blade, so you’ll need a workbench to hold the vise. Apart from that, there’s no other expense — apart from the file — and once you get good at using it, you should be able to sharpen a blade fairly quickly. Always remember to sharpen on the the push stroke; don’t use a back-and-forth sawing motion.

A simpler DIY alternative to a bench grinder that sharpens a mower blade fast is an angle grinder. It’s an aggressive tool, and if you use it the wrong way, heat buildup can damage the blade, leading to rougher cuts and shorter blade life. To avoid this, use a flap disc, rather than a standard diamond grit grinding disc, match the angle of the disc to the blade angle, and use light pressure. If you let the grinder do the work, it will get the job done more safely than if you force it. 

If you have a rotary tool, you’re almost ready to sharpen your mower blade. You just need a grinding accessory and a guide. This Dremel A679-02 Sharpening Attachment Kit, which is designed for Dremel tools, includes grinders and guides. Because the guide maintains the proper angle automatically, you can use this attachment to sharpen the blade even while it’s still on the mower. If you have a cordless rotary tool, you don’t even have to take the mower back to the garage for sharpening; you can do it out in the field.  

A rotary tool offers a smarter way to sharpen lawn mower blades, but if you don’t have one, you may prefer to buy something like the Sharp Pebble Cordless Lawn Mower Blade Sharpener, which is a rotary tool designed specifically for sharpening lawn mower blades. It will help maintain a sharp edge, but it isn’t a grinder you can use to restore a damaged blade. The guide can be adjusted between 20 and 40 degrees, so this tool will sharpen blades with angles other then the standard 30-degree bevel. You can use it to sharpen a blade without taking it off the mower. 

A drill is a common tool you probably already have, and if you’re wondering whether they make an attachment specifically for sharpening lawn mower blades, the answer is yes. The cenoz Crafts Man Lawn Mower Blade Sharpener is an example. This inexpensive attachment (a pack of five costs $9.99) features a grinding stone and a plastic guide that keeps the grinder at the proper blade angle. It actually grinds rather than simply sharpening the blade, and it’s easier to control than an angle grinder. This is a good choice if you have a drill, and you’re on a budget. 

If you’re looking for a manual sharpening tool that’s designed specifically for lawn mower blades, Smith’s 50603 Handheld Lawn Mower Blade Sharpener may be for you. It sharpens when you pull it along the edge of the blade, like a knife sharpener, and you can use it while the blade is still on the mower. If it sounds to you like such a tool would only be marginally effective, Amazon users disagree; almost 2,500 reviewers give it an average rating of 4.1 out of 5 stars. Keep this tool handy while you’re mowing to keep the blade in tip-top shape.