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How to Sharpen Lawn Mower Blades

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Difficulty Hard
Steps 5
Time Required 60+ Minutes
Tools Needed

Is your lawnmower struggling to cut tough patches of grass like it used to? Your blades may have dulled: fortunately, you can sharpen them back up again! Here’s what you need to know. Before we begin, you may want to know that we rate Greenworks Pro 60v – Most Durable Electric Mower, very highly for its excellent cutting abilities. For more of your gardening needs, take a look at our review of the Leaf plug and plant cannabis grower (super smart, super pricey).

1. First, Practice Safety

Make sure you have a thick pair of leather gloves to avoid any possibility of getting cut by a mower blade. Padded work gloves are important, because the blade may cut through thinner materials. If you love working in the yard, you may want to also look at the best string trimmer for your weeds. If your weeding job is a bit more difficult, grab the best backpack sprayer for reinforcement.

When you are working with the blade, you also really, really don’t the lawnmower turning on.

  1. Make sure the spark plugs are disconnected in gas mowers
  2. And the safety key and battery are both out in electric mowers. Now you are ready to begin!
Lawn mower blade sharpening angle
Mower blades are typically bolted on.

2. Make Sure You Have All the Right Tools

One more thing – make sure you are prepared with all the right supplies.

That includes a

  1. Socket wrench
  2. A clamping vise that you can use
  3. A file for sharpening the blade
  4. And a blade balancer…and it really helps to have at least a little experience using these things.

You can use a number of additional sharpening tools as well, depending on your preference, but a bench grinder may be a little difficult to use because of the awkward shape of the mower blade (difficult, not impossible, especially if you have experience with one).

3. Detach the Blade

  1. Lean the lawnmower over in a safe spot so you can easily access the blade. Lawn mower blades are held together with nuts: sometimes you may have to remove the whole assembly, but typically the blade portion is held on by a single nut-and-bolt arrangement.
  2. If your mower has multiple blades, you will want to detach each blade separately. These nuts tend to be large and very tight, for obvious reason. If the nut just won’t budge, then you may want to use some WD-40 or a similar oil to help loosen it up. If you need to brace the blade, grab the base where there should be no sharp edges to worry about.
  3. Once the blade is detached, you can take a close look at just how dirty it is. If it’s been a while since a cleaning, it may be caked with dried grass and dirt. Grab a hose and brush, and wash all this junk off. You want the blade to be absolutely clean before you begin.
Blade sharpening tool
Use a very light touch when sharpening the blade.

4. Clamp and Sharpen the Blade

  1. Place the blade in your vise and clamp it firmly, with the sharp edge of the blade facing outward. It’s important to clamp hard enough so that the blade won’t budget at all, but not so hard that it bends the blade in anyway – that could be disastrous when the time comes to reattach the blades.
  2. Sharpen the blade with your tool of choice, such as a file, drill-attached grinding stone, or another method. No matter what you use, sharpen very lightly, using long strokes for an even pattern on the blade.

Lawn mower blades are more fragile than they appear at first glance, and you don’t want grind out a damaging groove without realizing it.

5. Check the Blade Balance

How to sharpen a lawn mower blade with a file
A balancer ensures that mower blades remain balanced.

Once you have sharpened the mower blades until the edge has regained its cutting power, there’s one more important step to take.

You need to use a blade balancer to make sure the blade is properly balanced.

This is actually very important. If one of the blades is unbalanced, then the lawn mower won’t be able to spin the blades properly. This can cause bad vibrations (literally) and other problems.

If a blade appears to be unbalanced, then you will need to grind off a little more of the edge on the heavy side to lighten it up.

Note that this particular balancer shown is designed for dual-blade mower components with a blade on each side. Other balancers, however, are available.

When finished, detach the next blade (if necessary_ and perform the same process.

Once all blades have been sharpened, you are ready to re-attach them. Make sure you screw the nuts on firmly, with more or less the same pressure applied to each blade.

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