How to Sharpen Lawn Mower Blades with a Bench Grinder

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If your lawn mower has dull blades, it will coarsely rip through the grass, which will result in it leaving behind untidily torn tips on the ends of the grass blades. This, in turn, can make the grass turn brown, and also your lawn will become prone to diseases and pests. With dull blades, your lawn care will become even more difficult and more expensive all because you haven’t spent a little bit of time sharpening the mower blade.

It is necessary that you sharpen lawn mower blades at least once a year, but some people seem to think it is irrelevant. You might be thinking that the lawn mower will still cut grass even if the blades are dull, the point is that it will still cut the grass but not very well.

On the other hand, having a sharp blade will allow you to cut grass more easily and neatly, giving you a clean, healthy, and well-trimmed lawn.

Every year, before the start of the mowing season, ensure that you sharpen the blade of your lawn mower to enable efficient mowing. And if you’re frequently hitting rocks or the ground, then you really should consider sharpening the blade halfway through the season.

There are many ways to sharpen the blades of a lawn mower, such as using a bench grinder, rotary tool, angle grinder, or hand file. But in this guide, we are going to be focusing on how to use a bench grinder to sharpen the blade of your lawn mower.

Before you proceed to sharpen the blade of your lawn mower, first you need to know how to carefully remove the blade so as not to sustain any injuries or damage the lawn mower.

How to Remove the Blade of a Lawn Mower

The following steps will give you insight on how to remove the blade before you proceed to sharpen them. Depending on the type of lawn mower, you can sharpen the blade without having to take them off, which will save you a lot of time. But it is still advisable to take the blade off as this will allow you greater access to the cutting edges and grants you a better visual inspection of any damage to the blade, including stress fractures or extreme wear.

First, you have to disconnect the ignition wire from the spark plug. (If you own a cordless lawn mower, then remove the battery pack). This is done to prevent any accidental startup of the lawn mower’s engine. Also, ensure that you completely drain the gas tank, so that no fuel will be spilled when you are taking off the blades.

Locate the retaining nut or bolt that fastens the blade to the underside of the mower by tipping the lawn mower onto its side. Wedge a small wood block between the inner surface of the mowing deck and the end of the blade, this will help to keep the blade from turning. To loosen the nut or bolt, use a ratcheting wrench or socket. If the fastener is corroded and doesn’t come off, then apply some penetrating oil, wait for a few minutes and try again. Slip a metal pipe over the handle of the wrench in order to increase leverage when trying to loosen a specifically stubborn fastener.

The Blade Itself

When you have successfully removed the retaining nut or bolt, proceed to pull off the lawn mower’s blade. Ensure that you take note of the side of the blade that faces downward as it is highly imperative that the blade gets bolted back exactly the same way.

Now that you have taken off the blade, make sure you scrape the underside of the mowing deck clean with a narrow-blade puffy knife. Then, remove all the residue grass, mud, leaves, and other dirt. Ensure that you also clean the two sides of the lawn mower’s blade by spraying with penetrating oil first before proceeding to scrub with a stiff-bristle brush.

Using a Bench Grinder to Sharpen Lawn Mower Blades

A bench grinder is a small and useful machine that is bolted to a surface and comes with two grinding wheels, one on the left and another on the right. Both of the grinding wheels are spun at an extremely high speed. It is a sharpening tool that is used to trim off fragments of plastic, wood, or metal and can also be used to sharpen all kinds of blades.

Even most of the professional knife sharpeners who sharpen knives use bench grinders. It is better to get your knives sharpened because it is less expensive than getting a new one, the chefs are the ones that normally experience this because their knives can cost a whole lot to purchase.

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The DEWALT DW756 6-Inch Bench Grinder is a very nice pick to use for the sharpening of your lawn mower blades. It is easy to use and has a motor that runs at 3,450 rpm for high-speed material removal.

The following steps will give you an insight on how to sharpen your lawn mower blades using a bench grinder;

  • Before you start sharpening the blade of your lawn mower, make sure you wear safety goggles, as the bench grinder might fling tiny shards of the blade at very high speed and this could lead to injury.
  •  You would think that you are supposed to use a vice because of the high rate of speed that is associated with the bench grinder; ensure that you avoid using that because the vice will keep the blade in one place.
  • To sharpen the blade of your lawn mower, move it back and forth against the wheel of the bench grinder, and also ensure that you maintain the exact angle of the blade’s bevel when sharpening.  Also, when sharpening the blade, do not add a lot of force as this could lead to loss of control, and the blade might get chipped. So just set the blade on the bench grinder at an appropriate angle and let the grinder do its job.


If your lawn mower’s blade gets dull and you’re a handy person and want to get as much out of your blades as you can or you just don’t have the money for new blades, you can follow these easy and less expensive steps to sharpen it.