Weekend DIY: Sharpen your lawnmower blades

Keep your grass greener all summer long with a sharp mower blade

By Jay Somerset


1 comment

Cleaning a closet, sharpening chisels or running a batch of vinegar through the coffee maker–who said the DIY lifestyle was all glamour? In the name of efficiency and lifespan, sometimes you’ve got to slow down and sharpen up. Your lawn mower blade, that is.

With all the rain we’ve been having this summer, there’s a good chance you’ve been cutting like you’re living on the greens of Augusta. All this action, plus the rocks, sticks and other hard debris you’ve likely chopped up, dull your blade, making for an inefficient (more gas; more electricity), uneven cut.

Sharpening takes two hours and adds years to your mower’s life–the perfect weekend job. Here’s how to get rolling.

Remove the blade

Seems like a logical place to start. For gas mowers, wait till the tank is empty (to prevent spillage) or simply siphon the gas out. Remove the spark plug (so there’s absolutely no chance the blade will fire up), and flip the mower on its side.

Using a piece of wood, lock the blade so it doesn’t spin (a 2×4 end-cut works well) Then, wearing work gloves and using a ratchet or combination wrench, loosen the bolt (or bolts) anchoring the blade to the drive shaft. If it’s stuck, gently force it by using a little lube or by smacking the wrench with a rubber mallet, careful not to slip and fall onto the blade. (Note: if a family member sees you do this, they will assume you’re working hard and will bring you a cold drink.)

Sharpen the blade

OK, let’s get real here: there are two ways to sharpen a blade. The fastest way is to simply hop in the car and have the local hardware store do the deed for $10. It’s July, it’s hot–do you really want to fire up the bench grinder?

If you answered yes, you’ll need either a bench grinder (if you don’t already have one, consider picking one up; great for sharpening all tools, an electric bench grinder should be in every woodworker or DIYer’s toolkit) or a metal file. Hold the blade at the correct angle, careful not to dance around and potentially cut yourself or damage the blade, and sharpen away.

Reattach the blade

Just as you removed it, remount it. But, like that old adage measure twice, cut once, check that it’s rotating in the right direction. If you’ve forgotten, the blade wings should orient up toward the mower deck.

Tighten all the bolts, spin the blade, put the spark plug back in and get cutting. After that cold drink, of course.

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Nov. 29, 2011

10:15 am

You should also check the balance after sharpening by using a blade sharpening kit. This would prevent excessive wear on the shaft seal which usually results in oil leaks.

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