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DIY: How to Sharpen Your Lawn Mower Blades - Sears

DIY: How to Sharpen Your Lawn Mower Blades

Sharpening a Lawn Mower Blade

A properly maintained mower can help make your job easier throughtout the growing season. Before you change the oil, filter and spark plug and fill your mower with gasoline, you'll want to make sure that the blade is sharp enough to slice through grass effortlessly. This can lead to a healthier, cleaner looking yard all season long. Read on to learn the best way to sharpen lawn mower blades for your equipment.

What You'll Need:


Step 1: Put on Safety Gear & Remove the Mower's Spark Plug

Before you begin working on sharpening your lawn mower blades, taking proper safety precautions is an absolute must. Start by wearing thick safety gloves that can help keep your hands clean as you work and prevent nicks, cuts and scrapes.

You'll also want to wear safety goggles or glasses throughout the project, especially while sharpening the blade. After you're properly outfitted, make sure to disconnect the spark plug cable to prevent the mower from accidentally starting mid-project.

Step 2: Position the Lawn Mower & Remove the Blade

Unless you want to deal with spilled oil and gasoline, you'll want to work on sharpening your lawn mower blade before performing any other tune up projects for the season. Start by tipping the lawn mower with the spark plug side facing up to expose the underside of the mower deck and the blade itself.

Use your 2 x 4 block of wood to fix the blade in place so that it doesn't rotate while you remove the fasteners in the center with an adjustable wrench or ratchet and compatible socket. Like with other DIY maintenance projects, be especially careful not to strip the fasteners as you work.


Lawn mower on grass

Mower blade

Step 3: Sharpen the Blade

After you've removed the blade and set the fasteners aside, you have a couple options for sharpening the blade itself. The most straightforward technique is going to require a metal file and a bench vise. Use the bench vise to firmly secure the blade in place, then apply the metal file to the sharpened side of the blade, being sure to move the file only in one direction.

Continue filing until any chips and divots are removed. You also want to avoid over sharpening the blade, which can cause it to be damaged more easily. More experienced craftsmen can save time by using a bench grinder for this process.

Step 4: Check the Balance

Once both sides of the blade have been adequately sharpened, use your lawn mower blade balancer to check that the weight is evenly distributed throughout the piece. If too much was taken off one side or the other, the blade will appear lopsided.

Identify the heavier side of the blade by finding which end hangs lower, then take the blade back to the bench vise or bench grinder and remove some material from the unsharpened side of the blade and check the balance again. Repeat this process until both sides of the blades rest evenly on the balancer.

Step 5: Reassemble the Lawn Mower

After your blade is sharpened and balanced, simply reattach the piece using the fasteners you removed in the first step, flip the mower back over and reconnect the spark plug.

Lawn mower balanced on ground