Sharpen Lawn Mower Blades With A Budget-Friendly Solution From Home Depot

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Sharpening a lawn mower blade may seem like a difficult task that requires an expensive machine or years of experience, which is why paying a hardware store to do it for you may seem like the easiest answer. But if you're looking to save some money with a DIY solution, sharpening a lawn mower blade is actually pretty easy with a simple hand tool. A simple hand file, like the Nicholson 8 in. Rectangular Double/Single Cut Handy File (around $10 at The Home Depot), is a budget-friendly way to reshape the dulled cutting edge of a lawn mower blade to make it as sharp as it was when you bought it. This specific file has two differing faces; one called a single cut where the teeth are ground in a single cut across the face of the file. The double cut has two sets of grooves creating triangular teeth that cut more aggressively.

That being said, the cutting edge of a lawnmower blade needs to be different than a knife. If you were to sharpen a mower blade as thin as a knife, the edge would easily get nicked and chipped, so instead, the bevel of a mower blade should be ground (most commonly) to 45 degrees. This angle puts more material behind the edge quickly to keep it from deforming, as a thin blade would do. Your goal is to file the 45-degree bevel very smooth to create the sharp terminal edge of the bevel.

Never sharpen the blade while it's still on the mower and always use gloves and eye protection as you work. Before you remove the blade, disconnect the spark plug wire (on a gas mower) or remove the battery (on an electric mower). If the blade is bent, chipped, or damaged in any way, it must be replaced. If no damage is present, clamp the blade in a vise with one bevel accessible. Mower blades can be flat or have a gull wing shape to them, sharpening the bevel is the same on both. Dull blades have a ground surface that ends with a blunt edge, perhaps with small nicks present. Your goal is to use the file to evenly file away metal, keeping the bevel angle of the ground edge exactly the same.

Files cut as you push them. Put the double cut file face flat on the ground bevel of the blade (as shown above), pushing the file away and removing a small amount of metal. Don't focus on just the terminal cutting edge of the bevel, it will become sharp as you remove material evenly across the whole bevel. When you get a sharp edge on the blade, switch to the single cut file face to smooth the bevel, thus making it sharper.

When sharpening a lawn mower blade, keeping the blade balanced is important. Test the balance by hanging it from its arbor (mounting hole) on a small nail. If the blade rotates to one side, file away more metal from that side. When using a hand file to sharpen, this is usually not a problem