How to sharpen lawn mower blades

Sharpening lawn mower blades at home

Like anything with a sharp edge, lawn mower blades gradually grow duller with normal usage. Over time, blades also get nicked and dented by the small stones, sticks, tree roots and curbs the mower runs over. Even if your mower blades aren’t damaged, experts say you should sharpen your blades at least twice a year or more often if you mow a big lawn or have a long growing season. But you don't need to take them to a shop to have them sharpened. Here's how to sharpen lawn mower blades yourself.

In this article: Dual-Purpose Clamp-On Universal Vise, Smith’s 50603 Lawn Mower Blade Shop Essentials and Sharpal 103N All-in-One Garden Tool Multi-Sharpener

What are the signs my mower blades needs sharpening?

Your mowing experience

• Time: Is it taking longer to mow because you have to go more slowly and mow the same areas more than once?
• Effort: If yours is a push mower, is it harder to push it through unmown grass than when it was new? 
• Engine sound: Do you hear your engine bogging down and stalling when you get to a patch of thick, heavy grass?

Your lawn

• Lawn height: A dull blade provides inconsistent, uneven cut heights, so your lawn looks choppy and uneven.
• Grass color: Parts of your lawn appear brown and yellow instead of green, especially at the edges.
• Grass tips: Because dull blades don’t cut cleanly, the tips of your grass appear torn and frayed instead of sliced cleanly. 

Your mower blade

• Dents and nicks: When your mower blade hits something hard, something’s got to give, and it’s often the blade. Minor dents and nicks can be sharpened, but major ones call for blade replacement.
• Bent blade: Blades that have hit too many hard objects get knocked out of balance, putting stress on your mower's mechanical parts. Bent blades should be replaced, not just sharpened.

How do I get started with lawn mower blade sharpening?

Be safe

After gathering everything you need, disconnect your mower’s power source. If you have a gas-powered mower, remove the spark plug. If you have a battery-powered mower, remove the battery.

Tip the mower on its side

With a gas mower, be sure that you keep the carburetor side up so oil and gas won’t drip into your air filter.

Mark the blade

Mower professionals say the biggest mistake most people make when sharpening their own blades is putting them on backward. This means your blade won’t cut at all. Save yourself the trouble by using paint or a marker to indicate which side is up and which is down.

Remove the blade

First, spray some WD-40 or other lubricant to loosen stubbornly tight and corroded nuts and bolts. Then loosen the attachment nut and bolt, remove the blade and set the mower back on its wheels.

Clean the blade

Use old rags to remove caked-on dirt and grass clippings.

File the blade

Always file in the direction of the original cutting edge, and always file from the top to get the longest-lasting edge. Exert pressure only on the push stroke, not the pull.

Check the balance

When you sharpen your mower blade, you are removing metal from it. Unbalanced blades cause vibrations that can ruin your blade shaft and bearings, so hang your blade horizontally on a nail on a wall and see if it balances evenly. If it doesn’t, file a little bit more off the heavy side and check the balance again.

Reinstall the blade

Another common mistake amateurs make is not sufficiently tightening the bolt that holds the blade on. This is a very dangerous situation, so tighten, double-check and tighten again to keep yourself and your equipment safe.

What you need to buy for sharpening lawn mower blades

Gather everything you need before you begin so your work proceeds without a hitch.

• Gloves: When working around machinery, especially those with sharp edges, always wear a pair of work gloves. 
• Tools: Box or open-end wrenches are suitable for removing your blade; a socket set and ratchet are even better.
• Lubricant: Nuts and bolts on lawn mowers can be hard to loosen, so make sure you have a can of something like WD-40 to spray on hardware before you try to loosen and remove things.
• Rags: Mechanical activities can get messy quickly, so always have some old rags around.

Best lawn mower blade sharpeners and tools

Bench vise

Dual-Purpose Clamp-On Universal Vise

The safest way to sharpen your mower blade is to clamp it firmly in a vise attached to your workbench. Fasten this high-grade steel vise to your workbench, press the quick release button, push the jaws together and clamp without any need for locking screws.

Blade removal tool

Kintle Universal Mower Blade Removal Tool

You can use the easy-turn clamp handle to hold the mower blades securely in place while you loosen the attachment nut and bolt and again when you tighten it.

Files

Smith’s 50603 Lawn Mower Blade Shop Essentials

Clamp your blade firmly in a vise and sharpen it with a few easy pulls. The wire bristle cleaning brush stores inside the oversized handle, which is designed for easy use while wearing gloves.

Sharpal 103N All-in-One Garden Tool Multi-Sharpener

This tool not only sharpens your mower blades but also removes burrs and nicks from all your other sharp-edged garden tools.

Blade sharpener

All-American Sharpener Model 5005 Gen 2

Insert this lawn mower blade sharpener in your vise and adjust the angle to hold your blade in the perfect position for grinding. The four adapter pins secure most grinder models to the sharpener assembly.

Grinders

Bosch 4.5-Inch Portable Power Angle Grinder

Weighing less than 3 pounds, this epoxy-coated grinder has a 6-amp motor that produces 11,000 rpm. The side handle makes it easy to maintain the ideal angle while grinding. You can also use it to sharpen all your yard tools. 

Oregon 88-205 Lawn Mower Blade Sharpener and Grinder

The 1/3-horsepower motor turns quietly at 1,750 rpm. This 41-pound bench grinder adjusts to different heights and uses grinding stones to put a sharp edge on your mower blade.

Prices listed reflect time and date of publication and are subject to change.

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