How often to sharpen mower blades is an essential part of keeping and maintaining the health and tidiness of your lawn. Based on research, you should sharpen your mower blades after every 20 to 25 hours of use on average.

How Often To Sharpen Mower Blades

Let’s dig into this answer and learn the things you should know when sharpening your lawn mower blades, how to sharpen them, and the advantages of doing this regularly.

How Often Should You Sharpen Your Mower Blades?

You should sharpen your lawn mower blades weekly, according to research indicating that 75 percent of lawn care professionals do that. A good rule is to sharpen them after every 20 to 25 hours of running time. Just do the math to easily calculate and monitor your lawn mower usage. 

– How to Calculate When You Should Sharpen

Let’s say it takes you an hour to mow your yard, then you will need to sharpen your lawn mower blades after doing 20 to 25 cuts. However, it still depends entirely on how often and how many hours you spend using your lawn mower.

It is important to know how often you should sharpen mower blades as this would entirely affect your goal of maintaining a healthy and green lawn. While your lawn mower will continue running even with dull blades, you should not ignore it.

– Your Lawn Will Give You Clues

Your newly cut lawn grass will actually give you a sign when it is the time for you to sharpen your mower blade. You will notice frayed brown edges on the tips of your grass, which means you have used dull mower blades that did not actually cut the grass but tore it instead. 

Mowing using sharp blades will give your grass a neat and clean cut. However, using dull blades will make it look like the grass was being pulled or ripped with force. This will undoubtedly cause damage to your turf.

Using dull mower blades might also cause infestations and diseases. As you mow your lawn, your grass needs a short recovery time. If you use sharp mower blades that give your grass a nice clean cut, it will make the recovery time short. Consequently, your grass will have an easier time bouncing back.

When you use dull blades, your grass would need a longer recovery time, resulting in your grass being prone to numerous diseases or infestations and affecting its growth. So, instead of eventually fighting any disease or nuisances in the future, pay attention to your lawn mower blades, and make sure to get them sharpened regularly!

– Using Dull Blades

Dull blades will wreak havoc on your yard, as well as your pocket, over time.

Using Dull Blades

Using a lawn mower with dull blades will cause more harm to your grass than you realize, whereas maintaining the sharpness of your mower blades will cost you less in the end.

– Hard Surfaces

Another thing to consider when sharpening your mower blades is if you are mowing and the blades accidentally come in contact with hard surfaces, such as rocks, which might damage your blades and affect their performance.

Hard Surfaces

Keep in mind that you should always inspect your mower blades and see if they look worn and tattered.

– When You Need To Sharpen or Replace

Now, you might be confused about whether you should sharpen or replace your lawn mower blade. It might be time to inspect your lawn mower blades carefully and see whether there are signs that you should perform either of the two.

The rough brown or yellow tips you noticed on your grass are the results of blunt mower blades, so to easily determine whether your blades can be repaired by sharpening or if they need to be replaced, you will need to remove your mower blades from the lawn mower.

Your lawn mower blades need to be sharpened after 20 to 25 hours of use, as we have mentioned above, but eventually, after suffering serious damage over time, you may need to replace your blades with new ones. However, do not worry if the need to replace the blades arises. Replacing your blades prevents harm to your grass, makes mowing easier and safer, and costs you less. So, we list down below the four indicators to know if your mower blades need to be replaced immediately.

  • Mower blade is more than two years old

First, consider how old your mower blades are. If they are more than two years old then, it is already time to replace them.

  • Mower blade is bent

Second, if your mower blades are bent, which commonly happens if they often hit hard surfaces, then it is time for a replacement.

Mower Blade is Bent

This occurrence affects your mower blades’ performance and efficiency, resulting in uneven cuts and damaged grass. This is also a safety-related issue as it might damage your lawn mower prematurely.

  • Mower blade is blunt or dull

The third sign is if the blade is blunt, even after you have sharpened it twice. While sharpening is important, doing this frequently will make your blades brittle and weak, so you may need to replace them if that’s the case.

  • Mower blade has major damage

Lastly, if you observe that there is major damage to the blade, such as deep dents, cracks, and gouges, and there are missing pieces, you should replace it.

Mower Blade has Major Damage

This case might cause serious harm, such as fatal freak accidents, as objects can be easily propelled at high speed.

How Can You Sharpen Your Mower Blades?

To sharpen you mower blades, you need to follow certain steps, although they will differ slightly for different types of mowers. 

You need to first disconnect any kind of power supply, park it on a flat, level surface, and prepare tools for the easiest way to sharpen lawn mower blades.

– Sharpening Riding Mower Blades

The first thing to keep in mind when sharpening riding mower blades is that it cannot start by accident. You can either drain the fuel or remove the spark plug boot, pulling away the rubber boot that is attached to the spark plug wire to prevent it.

Second, you will be required to prepare the following materials or tools to make this process a lot easier: safety glasses, work gloves, socket wrench, two-by-four piece of wood, vise clamp, hand file, nail, and marking pen.

To start doing the actual process, make sure your riding lawn mower is parked on a flat, level surface. Adjust the mower deck to the highest setting, and lay it down on the floor. Keep yourself safe by wearing safety glasses and gloves to protect your hands before laying down on the floor and positioning yourself under the deck.

For easier installation of the blades, mark the bottom of the blade using a marking pen. Look for a spindle bolt; it can be found at the center of the blade. Using the two-by-four piece of block, wedge it inside the blade and the mower blade. Get the socket wrench, and use it to loosen and remove the spindle bolt. Then, remove the blade under the mower deck.

To sharpen, place the metal file against the cutting edge of the blade. Start filing until the edge of the blade becomes sharp again and you see shining metal appearing. Turn to the other side of the blade, and start filing again until it is all sharpened.

– Sharpening Lawn Mower Blades With a Grinder

After gathering all the tools needed, wearing safety materials, positioning your lawn mower, and removing the blade using the socket wrench as we mentioned above, place the blade on a working table that can hold it in place. Then, work on one side of the blade at a time.

How to Sharpen Lawn Mower Blades With a Grinder

Use an angle grinder with a grinding stone disk to fit the blade in place. Work on sharpening by holding the grinding disk perpendicular to the thin edge of the blade and running it along the blade to smoothen the nicks.

Keep checking your work from time to time to see whether the edge is sharpened enough or it needs more filing as a mower blade sharpener will remove the metal quickly. If you notice that a layer of clean metal shows and the edge is sharp, you can reinstall the newly sharpened blade on the lawn mower, and it’s ready to use.

– Sharpening Blades Without Removing Them

If you want to sharpen your mower blades but do not have the time to remove them, sharpening without removing it is possible. You will need to gather the following materials and tools: Safety glasses, gloves, a wire brush or anything that can help you scrape the dirt attached to your mower’s deck and blade, scrap wood, and an angle grinder or a mill file.

After preparing all the tools you need and wearing the safety gears, you can now place your lawn mower on a flat surface. Start working on disabling the power supply to avoid starting your mower accidentally, and then tip it down properly. You can kneel down to easily brace the mower using the scrap wood, and scrape off the dirt that had accumulated on it. 

Next, lock the blade in place, and start grinding one edge of the blade. Keep in mind that you must maintain a 45-degree angle to make your blade sharp, and work away from the center of the blade. Do the same process on the other side of the blade, after which your lawn mower will be all settled.

– Using the Best File for Sharpening Lawn Mower Blades

The bastard cut mill file is one of the best and most recommended hand flat files you can utilize to sharpen the blades of your lawn mower easily. It is a 10-inch to 12-inch mill file used by manually filing the blades of a lawn mower.

It is made out of high-carbon hardened steel that makes it long-lasting and effective for removing the material quickly. It also has a plastic handle that makes it easier to hold when working on the edges of your blades.

A bastard cut mill file is a must when maintaining your yard and keeping your lawn mower running smoothly. When using a bastard cut mill file, sharpen and polish the blades’ edges by making sure you keep the right angle of the file. In less than ten minutes, you will have a newly sharpened blade that’s ready to gracefully mow your yard more efficiently than ever!


Understanding how often to sharpen your mower blades will keep your grass in perfect condition and your yard tidy. Here are the things to remember about when to sharpen your mower blades:

  • Sharpen the blades after every 20 to 25 hours of lawn mower usage.
  • If you notice that the grass looks frayed rather than having a clean cut, then it’s time to sharpen.
  • If your yard has started browning and yellowing mysteriously, consider sharpening your mower blades.
  • When the blades hit a hard surface while in use, sharpen your blades immediately.
  • If your blades are sharpened at least a year ago, it’s time to sharpen them again.

Regularly sharpening your lawn mower blades will make your yard a happy place and your mowing experience a safe and easy one.

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