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How To Sharpen Your Lawn Mower Blade Without Removing It? (2023 Guide)

By: Rhiannin Bunney

how to sharpen lawn mower blade without removing

Keeping your lawn mower blade sharp is critical to keeping your lawn looking as good as possible.

Not only do sharp blades cause less damage to the grass you’re cutting, but they also do a more even job which helps to keep your lawn looking better after you’ve finished.

Of course, grass doesn’t cut easily and is full of little silicate particles that dull your lawn mower’s blade over time.

That means that you need to sharpen your lawn mower blade regularly if you want to maintain peak performance and keep your lawn as healthy as possible.

You could send your lawn mower’s blade a professional to get it sharpened, or pay for replacement. Or, you can go the more cost-effective route and sharpen it yourself at home.

You can even sharpen your lawn mower blade without having to remove the blade from the lawn mower. This guide will show you how, though I still recommend taking the blade out for a more complete sharpening every once in a while.

In this guide you’ll learn:

  • How to sharpen your lawn mower blade
  • Why it’s important to sharpen your lawn mower blade
  • And much more!

Why Do You Need To Keep Your Lawn Mower Blade Sharp?

Grass has evolved to have small silicate particles embedded throughout the leaves. It evolved that way to help discourage herbivores from eating the leaves as they grow. Even though that adaptation wasn’t very effective, there are still plenty of herbivores who are capable of eating grass, it has a big impact on the tools we use to keep and maintain our lawns.

The biggest impact of those silicate particles is that lawn mower blades dull rather quickly compared to other blades. Your lawn mower’s blades don’t have to be incredibly sharp to be effective, but once they get too dull they start tearing and shredding your grass instead of cutting it.

Once your lawn mower blade has started shredding your grass, it’s harder for your grass to keep your lawn growing. You may even start to see yellow-green tips and other signs of disease in your lawn. That’s because ragged ends are harder for your grass to close, harder to heal, and more vulnerable to infection.

Read More: >> The Best Lawn Mower For Hills

Keeping your lawn mower’s blade sharp is also important for the lawn mower itself. A dull blade can put more stress on the moving components of the lawn mower, including the motor, leading to higher maintenance requirements and more expensive kinds of maintenance over time.

Keeping your lawn mower blade as sharp as you can is a good way to make sure your lawn and your lawn mower are in the best possible condition.

Are you comfortable taking your lawn mower’s blade off? This video shows how to sharpen a removed blade. It also gives some good tips for how to get your lawn mower ready and when to sharpen your lawn mower’s blade.

How To Sharpen Your Lawn Mower Without Removing It: 5 Step Guide

Tools You’ll Need To Sharpen Your Lawn Mower Blade Without Removing It:

  • A Flat File OR A Rotary Sharpening Tool
  • Your Lawn Mower
  • a Clamp for Another Way to Prevent the Blade from Moving
  • a Shop Rag
  • a Mild Cleaner
  • Lubricant OR WD-40

Of these tools, the flat file or rotary sharpening tool are probably the rarest. However, both are useful for more than just sharpening the lawn mower blades so it may be worth investing in a set if you don’t already have some.

Read More: >> How To Mow Your Lawn Like A Professional

Other than that you should already have everything you need. The cleaner, and lubricant or WD-40 are both optional. Both can help make your job a little easier, and help your lawn mower blade last a little longer. But, you can sharpen your lawn mower blade without them if you need to.

Step 1: Get Your Lawn Mower Ready

The first step is to get your lawn mower ready. Mostly, that means making sure it’s not connected to any power sources, and that it’s in an area where you can easily turn it on its side and reach the blade underneath.

I recommend moving your lawn mower onto a tarp or a sheet to help make cleanup easier if there are any grass clippings stuck underneath the lawn mower.

If you have a battery-powered lawn mower, now is the time to disconnect the battery. If it’s a cord-powered lawn mower, unplug the power cord. For gas-powered lawn mowers you should remove the spark plug.

Step 2: Seal The Gas Cap

If you have a gas powered lawn mower, I recommend either draining the gas tank entirely, in addition to removing the spark plug. You should also seal the gas cap with a bag, or just by placing a rag around the gas cap to help prevent accidental spills or fumes escaping the gas tank while you work.

Step 3: Prevent Your Lawn Mower Blade From Moving

The next thing you need to do to be able to sharpen your lawn mower blade, without removing it from lawn mower, is to make sure it can’t move while you’re working.

One of the easiest ways to stop the lawn mower blade from moving is to use a wooden block, or other large obstruction, to hold it in place once your lawn mower’s on its side. You can also use a clamp to hold the blade in place in some lawn mowers, but not all designs support a clamp.

However you block your blade in place, check and make sure it really isn’t moving. While lawn mower blades don’t tend to be particularly dangerous moving at slow speeds, the last thing you want is a sharpening accident.

Step 4: Clean The Lawn Mower Undercarriage

Once the blade is locked in place, you should take this opportunity to clean out the bottom of your lawn mower. Clean lawn mowers are more effective, tend to be able to move faster, and put less stress on the lawn mowers motor.

A shop rag and simply cleaning solution is all you should need. Scoop out any remaining grass clippings, mulched leaves, and twigs, and then gently clean the bottom of the lawn mower around the blade.

If you use any water during this process, make sure the undercarriage of your lawn mower is completely dry when you stop. If you leave the metal wet, it’s more likely to rust and corrode over time.

Step 5: Sharpen Both Sides Of The Blade

Your blade has two halves leading out from the center attachment. Each half has its own cutting edge that needs to be sharpened. Since the blade is still installed in the lawn mower, you’ll only be sharpening the closer side of the cutting edge. I recommend sharpening this way because it’s faster, easier, and single bevel blades work just as well.

Sharpening a single side of your lawn mower’s blade’s cutting edges will get them just as sharp, and takes less work than trying to sharpen both sides. You won’t have to reach around some pretty tricky angles to sharpen the side that’s facing the lawn mower’s cutting deck. 

What is the difference between the cutting edge and the blade? The blade is the whole part, the cutting edge is the small section on either side of the blade that is sharpened.

If you’re using a flat file to sharpen your blade it will take just a little bit longer. Run the file along the blade several times, only applying pressure in one direction. This will gradually take off a little bit of metal, sharpening the blade and making it more effective. It will probably take 5 to 10 minutes per side to sharpen the lawn mower’s blade this way.

If you’re using a rotary sharpening tool, the sharpening process should be much faster. Rotary tools take off metal more quickly, and are easier to use, but can be less precise than using a file.

It’s important to make sure your rotary tool’s tip is set to about a 45° angle since that’s the best angle for sharpening your lawn mower blade. If the sharpening tool is already set to the right angle you don’t need to worry about changing the angle while you’re working. Just put the tip against the lawn mower blade so that it’s flush with the blade.

Run the rotary tools sharpener down the blade a few times until the blade is visibly sharper. It should only take 2 to 3 repetitions and only a couple of minutes per side to get this done.

Once you finished sharpening the blade, clean up any metal shavings that are still on the undercarriage for on the lawn mower blade itself. Turn the lawn mower back upright and reconnect the power source and fill the gas tank if needed. You should be ready to mow with your freshly sharpened blade.

When Does Your Lawn Mower Blade Need Sharpening?

Knowing when to sharpen your lawn mower blade can be a little bit of an art rather than a science. That’s because different kinds of grass dull your lawn mower’s blade at different rates. Combine that with different lawn mower motors, different blade materials, and different blade designs and you have a recipe for very varied sharpening schedules.

There are some general rules you can follow to make sure sharpening the blade at the right time. These are good guidelines, but if you think your lawn mower blade needs sharpening you’re probably right.

Read More: >> The Best Lawn Mowers for Uneven Ground

I like to sharpen my lawn mower blade just as I’m starting to mow my lawn in the spring. It helps make sure my lawn is off to a good start every year, and also gives me a chance to look over my lawn mower for any signs that it needs maintenance before mowing season starts.

After that, your lawn mower’s blade should be sharpened every 20 to 25 hours of use. For some people, that means that you’ll only sharpen your lawn mower blade a couple of times a year. For other lawns, you may need to sharpen the blade several times a season. That’s why some guides, like this guide to lawn care, recommend sharpening twice a season.

Of course, the quality of your blade’s original edge and the quality of the material itself can impact how often the blade needs to be sharpened. High-quality metal and a well-ground edge will always last longer than than soft metal or a badly sharpened edge. Some grass types may also wear through your blade’s edge faster.

Because of that variability, I recommend you pay attention to your lawn mower’s performance on your lawn. If you start to struggle to get an even cut, it’s time to sharpen the lawn mowers blade. Pay attention to how long you can go between sharpening to develop your own customized schedule.

Just remember that the more often you sharpen your lawn mowers blade the more often you’ll have to replace it. That’s because sharpening takes off a small amount of metal every time. As you start to strip the metal away, the blade will get less effective and more brittle.

Eventually, after sharpening your blade several times, it’s better to just replace and get a new blade than to keep trying to sharpen it.

Don’t be surprised if your sharpening schedule changes when you change lawn mower blades. That’s the different metal qualities and blade edges at work. Even if you buy the same model of blade it’s possible that the manufacturer will have changed processes and that the new blade will need a different maintenance schedule.

My Final Thoughts On Sharpening Your Lawn Mower Blade Without Removing It

Keeping your lawn mower blade sharp doesn’t have to be difficult. Sharpening your lawn mower’s blade without removing it is quick, easy, and very effective.

It’s one of the simplest ways to keep your lawn mower’s blade in good condition without just replacing the blade.

Plus, your grass will definitely appreciate the sharper blade. It will be healthier, grow faster, and less vulnerable to disease when you keep your lawn mower’s blade in good condition.
So, now that you know how I know how easy it can be there’s nothing to get in your way.

Keep your lawn mowers blade sharp, keep your lawn mower effective, and enjoy your beautiful lawn.

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