Maintaining a sharp blade on your lawn mower is extremely important for keeping your grass in the best condition it can be. Dull blades struggle to slice through grass and tear it instead. This results in yellowing, disease, pests, and an all-around unhealthy lawn.
The best way to sharpen lawn mower blades is to first remove them from the mower and take care of the sharpening and balancing at the same time. However, some property owners aren’t able to get their blades off. This could be due to missing tools, excess rust, or maybe just a lack of time. Whatever the reason might be, it begs the question of how to sharpen lawn mower blades without removing them. Let’s take a look at if this is possible, and if so, how exactly to go about doing it.
Can a Lawn Mower Blade Really Be Sharpened Without Removing It?
Yes, you can sharpen a lawn mower blade without removing it. I usually take my blade off to sharpen it, but if you want to hone yours while it’s attached to the mower you certainly can. Since sharpening your lawn mower’s blade while it’s bolted on requires a bit of a different approach to normal blade sharpening, I’ve listed the steps you should follow below.
How to Sharpen Lawn Mower Blades Without Removing (Quick Summary)
- Disconnect your mower’s spark plug hood, cord, or battery.
- Tip your mower on its side (the right way).
- Brace the mower with a piece of scrap wood.
- Clean the blade.
- Block/lock blade in place.
- Starting on one side, grind the top edge of the blade. Make sure to grind away from the center at a 45-degree angle.
- Repeat on the other side of the blade.
- Make sure the blade is still securely fastened, and you’re good to go.
Sharpening Lawn Mower Blades Without Removing Them (Step By Step)
Now that I’ve outlined the process, I want to dig into the details of how to sharpen push lawn mower blades without removing them. While this may seem like a complicated process, it’s actually pretty simple. Anybody can sharpen their own lawn mower blade with the right equipment, so follow along and let’s get it done.
1. Gather Equipment
Before we get into how to sharpen lawn mower blades without removing them, let’s talk about what you’ll need to get the job done. Luckily this project only requires a few things:
- Cut-resistant gloves.
- Eye protection.
- Wire brush, putty knife, prybar, or other scraper to clean off the mower’s deck and blade.
- One or two pieces of scrap wood/something to brace the mower.
- Steel file, angle grinder, or drill (with a grinding attachment).
Once you have your supplies together, set your mower up on your workbench or somewhere flat where you can kneel down and work on it.
2. Disconnect Power Supply
Now, before you go any further, make sure that you’ve disconnected the source of power to your lawn mower. On electric mowers, this means either removing the battery or making sure that the cord is unplugged. If you’ve got a gas mower, all you will need to do is remove the spark plug hood from the spark plug. Doing this ensures that your mower won’t start unexpectedly.
3. Tip Lawn Mower Over
Once you’ve got your mower where you want it, you’ll have to tip it onto its side so that you can access the blade. This step is actually very important. A lot of people don’t realize that there is a right and wrong way to tilt your mower.
The correct way to tip your mower over is to do so with the air filter and carburetor facing up. This makes sure that gas and oil won’t leak out of their reservoirs and into places they shouldn’t be.
4. Brace/Support Mower
With your mower flipped onto its side, you’re going to want to make sure that it doesn’t accidentally fall down. I like grabbing scrap 2×4 pieces of wood I have laying around and placing them diagonally against the mower, but anything goes as long as it can adequately support the machine. Lawn mowers usually won’t go anywhere once they’re on their side, but it’s always a good idea to set up a little extra support.
5. Clean Mower Deck and Blade
Use this opportunity to scrape off every bit of debris on the underside of your mower that you can. It’s best practice to regularly clean your mower’s deck and blade, but like flossing teeth, let’s be honest and acknowledge that a lot of us don’t do it enough.
You can use a wire brush or whatever blunt object you have on hand to scrape all of the dried dirt and grass off the deck and blade. For stubborn patches of gunk, using a little bit of water can help a lot. I usually tackle the deck first and then move on to cleaning the blade. This can be tricky with the blade fastened in place, but do the best you can to get it clean.
6. Block/Secure Blade
Once you’ve finished cleaning the blade, it’s a good idea to secure it in place so that it won’t move while you’re trying to put a new edge on it. If you have a specialized blade lock tool, great, but I think that the easiest way to go about securing your blade is with a set of locking pliers or a block of wood. You’ll either have to lock the pliers onto one edge of the mower deck to stop the blade from turning, or find a piece of scrap wood that is the right length and can be wedged between the blade and one side of the mower deck.
Some people just hold the blade with one hand while they sharpen it with the other, but this can be dangerous, especially if you’re using a drill or angle grinder. Also, it is a lot more difficult to hone your blade at the correct angle if you’re trying to do it with one hand.
7. Grind Blade
After doing all of the necessary prep, it’s time to actually hone your blade. There are a handful of options when it comes to what to use to sharpen your lawn mower’s blade, but I recommend using what you’re most comfortable with and have easy access to. Whatever tool you’re using, to sharpen your blade there are three big things you need to do:
Grind only the “top” side of the blade at a 45-degree angle.
Here, the top side of the blade refers to the side that faces the engine of the mower, not the ground. When grinding, you don’t need to be at exactly 45 degrees. You should be able to follow the existing angle on the blade so eyeball what seems about right and go slow and steady.
Go in one direction: from the center out to the end of the blade.
It’s really important that you file or grind smoothly in one direction. Start at the back of the blade (near the center where it’s mounted) and gently hone the edge as you push out towards the end. You don’t have to be an artist, but avoid any kind of sawing or back-and-forth motion.
Try to remove the same amount of material on both sides of the blade.
Since you won’t be removing the blade to check its balance, try to sharpen both sides of the blade evenly. While there’s no way of knowing exactly how much material you’re removing from each side of the blade, you will need to make a rough estimation. Just keep track of how many passes you do with your file or grinder and try to replicate it.
A Few Things to Be Aware Of
Now that you’ve got the main idea of how to sharpen lawn mower blades without removing them, I should mention a couple of things to be aware of. Though it’s a straightforward project, there are some things you should look out for before you get started, while working, and after you’ve finished.
Should the Blade be Sharpened or Replaced?
Sometimes there’s no need to sharpen your lawn mower’s blade because you’re actually due for a replacement. Lawn mower blades don’t have a specific lifespan, but generally, they should be swapped out every 2 or 3 seasons. The best way to tell if this is the case for you is to take a look at your blade. If the blade is bent, has large nicks/dents, or is suffering some serious rust damage, you should probably buy a new one. Knowing when to replace lawn mower blades can save you a ton of time.
Sharpen Blades When the Gas Tank is Empty
Maybe you don’t have much of a choice, but if you can, it’s best to do this project when you’re out of gas. Since your mower will be tilted on its side for quite a while, it helps to do this after you’ve run the gas out of your mower. This will prevent gas from leaking anywhere it shouldn’t be. Chances of leaks are slim, but try and prevent them if possible.
Watch for Excess Vibration
Once you’ve got your blade sharpened, and you’re out cutting grass again, be aware of how your mower is running. If there is more vibration to the mower than you remember, you might have shaved your blade a bit out of balance.
When you run your mower with an unbalanced blade, you could end up with poor cut quality and even cause structural damage to the mower. If you suspect your blade is out of balance, you may want to take it off the mower and check. Balancing lawn mower blades is a pretty easy process and could save you some trouble in the long run.