How Do You Sharpen A Lawnmower Blade?

Do you have a dull lawnmower blade? Have you been cutting grass with your lawnmower and feel like it is longer than it should? Do you see raggedly cut grass? Well, you might need to check your lawnmower blades for their sharpness.

Ask any homeowner what the one most important tool that helps them in keeping their lawns well maintained is.

He or she would say it is their lawnmowers. Yet, frequently, it is these machines that are neglected when it comes to their maintenance. It’s easy to overlook blade maintenance as I tend to forget from time to time as well.

The blade is an essential part of the mower.  If it is in bad condition, it will affect your grass-cutting session. And the adverse effects are not just related to the look of your lawn. A ragged top cut on a leaf of grass opens up the grass plant and creates a perfect situation for grass diseases. Do you know the right cutting heights for grass?

Lawnmower blades often need sharpening. It is recommended to sharpen these blades at least two times every season using a good sharpener. Read this article to find out the injury dull mower blades can cause to your lawn.

This maintenance action would make it easy for you to maintain a green and healthy lawn. Keeping your lawn mower blade sharp is your first line of defense against lawn diseases.

In this article, we show you the techniques for sharpening your lawnmower blade.

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Learn How to Sharpen Your Lawnmower Blade

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Dull Blade to Sharp Blade

There are various methods used to sharpen a lawnmower, including the use of a hand file, bench grinder, angle grinder, or rotary tool. A lawnmower blade sharpener helps you make your lawn-cutting job faster and less stressful. Here, we provide a detailed guide for a lawnmower blade sharpener that works for almost all lawnmowers.

Tools for Sharpening Lawnmower Blades

Tools & Materials

  • Closed-end wrench
  • Dull Mower blade
  • Torque wrench
  • 10” file
  • Vise
  • Hammer
  • Nail
  • Gloves

For Professionals

Those who cut grass as professional service providers should invest in one of the high-end power tools designed and manufactured specifically to serve that purpose. These are called grinders and are usually the best choice for blade sharpener tools.

For Homeowners

Homeowners generally do less mowing compared to professionals and can select from various options available for lower-end power and manual tools. If you intend to save money, you can rely on the manual, traditional file. Most homeowners would find a file to be a great choice because they it typically costs under $20. The Nicholson file shown below is what I use.

nicholson flat file review for sharpening lawn mower blades
Get This File At Amazon for under $20

What You Should Know Before Sharpening the Blade

Regardless of which tool you use, before you start, you should know some essential things such as:

  • How sharp the blade should be
  • How frequently you should sharpen
  • When sharpening does not work

The cutting edge of the mower blade has to be sharp but not razor-sharp. If you sharpen it too much, the edge will not hold up for longer, and you will have to sharpen it again soon.

If you find large bends or nicks in your blade, the sharpening is not going to correct the issue. You should consider replacing your lawnmower blade instead.

Removing the Blade

Before you start anything, take note of the precautions you need to take. Remember, safety comes first.

Ensure your work area is free of any clutter, and you are using the proper socket size for the nut on your mower.

Tips for removing lawnmower blades:

  1. Read your lawn mower’s instruction manual
  2. Wear protective goggles and hearing protection. Gloves and long pants are also a must. Another safety recommendation is to wear sturdy close-toed shoes
  3. Ensure that you disconnect the machine from its power source. If it is a cordless mower, remove the battery pack. This precaution will ensure that the engine won’t start unexpectedly.
  4. Remove the spark plug especially if you sharpen the blade without detaching it from the mower

We recommend removing the blade before sharpening. However, it depends on the design of your mowing equipment, and whether you can sharpen the blades without removing them.

Removing blades can save you a lot of time. But removal provides better access to the blade’s edges. It also facilitates better visual inspection of any existing damage that occurred on the blade, such as excessive wear or stress fractures. Moreover, consider emptying the gas tank so that no fuel spills when you remove the blade.

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Use a wooden block to prevent the blade from spinning when you loosen the nut.

Next, turn the mower on the side that exposes the bolt or nut securing the blade to the mower. Use a short wooden block between the inside surface and the end of the mower blade to keep the blade from turning.

With the help of a long-handle wrench with a socket, loosen the bolt or nut. If you find that the bolt is rusted or stuck, use some penetrating oil and try again after a few minutes. Use a metal pipe over the handle of the wrench to get more leverage when loosening a stubborn bolt.

Once you remove the retaining bolt or nut, remove the mower blade and remember which side of the mower blade faced downward. This identification is essential to make sure the blade gets installed back in the same position. Use a permanent marker to mark the side that you need to remember.

Cleaning and Positioning

After you remove the blade, spend some time inspecting and cleaning the underside of the deck with the help of a knife with a narrow blade. Make sure all mud, grass, leaves, and debris are removed from it. Use penetrating oil and a stiff-bristle tool, such as a brush, and clean both sides of the blade.

Mower blades generally have a cutting edge on both ends located on opposite sides of the blade. These cutting edges are only 3-4 inches long and don’t extend the blade’s length. So, you can clamp the mower blade in a vise in an angular position with any one of the cutting edges facing upwards.

Blade Sharpening

Get a blade sharpener that works with a drill to sharpen your lawnmower blade. This tool has an abrasive stone, a steel shank, and a flat sharpening guide.

The surface of the stone is beveled and grinds the right cutting angle for the blade. Watch this video demonstration to see how to sharpen your blade properly.

How to ● Sharpen a Lawn Mower Blade ● short and sweet !

To use the sharpener, chuck the stone into the drill and wear safety glasses. Power the drill machine on and operate it at the maximum speed.

Now, place the sharpener over the edge of the mower blade. You should ensure that the dull side of the blade rests against the stone’s beveled surface and that the flat surface faces the back of the blade.

Move the stone back and forth slowly with medium pressure along the cutting edge. Check the blade’s sharpness after 4-5 strokes. Repeat the step if necessary until the blade appears sharp. Then, take the blade off the vise and turn it to begin sharpening the opposite edge.

Blade Balancing and Reinstalling

Once you have sharpened both the cutting edges of the blade, the next step is to balance it. When you sharpen the blade, there are chances that more metal is removed from one end as compared to the other, and you get an unbalanced mower blade. Using such an unbalanced blade for mowing can result in excessive wobbling, thus damaging the motor and putting unwanted pressure on the mower.

There is a great way to check if a mower blade is balanced. Slip the center hole of the blade over a nail on a wall. Keep the blade in the horizontal position and see if it remains level. If one end rotates down towards vertical, you can determine that it is unbalanced.

In this case, you can consider sharpening the heavier side to remove extra metal and retest it to get a balanced blade.

Though this nail technique works and is a simple method, you can use a mower blade balancer for more accurate results. It is a cone-shaped, multi-tiered metal fixture that can be placed on a flat surface with a blade set on the top.

This tool works with a blade with a varying diameter of center holes. When you use a balanced blade, it remains level; otherwise, it tilts towards either side, indicating the heavier side of the blade that needs more sharpening.

Once you sharpen and balance the blade, reinstall it into the original position on the mower and tighten the bolt. Use a wrench to ensure to tighten the bolt snugly. Attach the wire again, fill the gas tank, and put your freshly sharpened mower blade to test.

3 thoughts on “How Do You Sharpen A Lawnmower Blade?”

  1. Hi Alex, Thanks for the great information. Anyway, which type of lawnmower cuts grass best; a modern motorised mower with spinning blades or the older manual style mower with rotating blades?


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