When you buy a lawn mower, the blades are sharp and ready to cut the grass. Over time, the blades will wear and become dull so, as part of your lawn mower maintenance, you will need to make sharpening lawn mower blades a top priority. But what is the best grit for sharpening lawn mower blades?
If you are using a grinding wheel then the best grit for sharpening your mower blades would be between 60 and 80. However, if you are using a file then you will need to start with something coarse before moving onto a medium then fine grit in order to get the best results.
If you’re new to sharpening lawn mower blades or simply want to learn more about the best approach in terms of grit then you’re in the right place. In this article, we will cover everything you need to know to confidently and effectively sharpen the blade so your mower performs at its best.
When it comes to sharpening your mower blades, a grinding wheel is almost always going to be the best choice. These tools offer efficiency and ease of use particularly when you compare them to other methods like files.
The type of grinding wheel you need to use for your mower blades will depend on what they are made from. For example, if your lawn mower is fitted with an iron or steel blade then an aluminum oxide grinding wheel is going to be your best bet. On the other hand, if your mower uses a softer material such as brass, then a silicon carbide grinding wheel will do the job better.
Choosing the right type of grinding wheel for the material your blade is made from will ensure the best results in the shortest amount of time. While lawn mower maintenance is a must, we don’t want to make it more difficult than it needs to be.
Regardless of the type of grinding wheel you’re using, you will need to make sure that you keep it at a consistent speed. This can be anywhere between 5000 and 6500 feet per minute.
Harder Material Blades
Some lawn mower blades are made from hard materials like iron or steel. In this case, you’ll want to make sure to use an aluminum oxide grinding wheel. Fortunately, these are extremely common and so very easy to get your hands on. Not only are they great for this but they’re also perfect for working with a whole host of other materials including stainless steel and bronze.
One of the best things about aluminum oxide grinding wheels is that they are so durable. When you are working with harder metals, this is a super important characteristic and will prevent you from having to replace the wheel unnecessarily.
Soft Material Blades
Other lawn mowers have much softer blades and may be made from metals such as brass or gray iron. In this case, you’ll want to choose a silicon carbide grinding wheel as, while it is harder than aluminum oxide, it’s also much more abrasive.
Can You Use A File To Sharpen Mower Blades?
What happens if you don’t have a grinder? Maybe you just fancy using other tools to sharpen your lawn mower blade. In that case, you might choose to use metal files and this is a perfectly acceptable way of doing things.
However, if you are looking for a fast method of sharpening lawn mower blades, we wouldn’t recommend files as a go to as it is a much slower process.
When you start sharpening, you will need to make sure that you use a coarse file before moving onto medium or finer files for the final few passes.
A lot of people wonder which are the best types of files for sharpening lawn mower blades but in truth, any of the most common types are fine. You don’t need to throw a load of money at super expensive files and the kits you can buy online are usually more than sufficient.
Can You Use Sandpaper To Sharpen Mower Blades?
It might seem as though sandpaper could be a good choice for sharpening lawn mower blades but this is one of the most impractical options. I mean, if you think about it, sandpaper is very similar to the material used on power sanders but when doing the job manually, you just aren’t going to get the same rigidity and speed needed to effectively sharpen the blade.
You could spend hours laboring over the blade with a piece of sandpaper to no avail so why would you when other options make so much more sense? But it’s easy to see why people might think that this is an option so if the thought has crossed your mind, don’t kick yourself.
Can You Use An Angle Grinder To Sharpen Mower Blades?
An angle grinder is a powerful tool that can make light work of sharpening your lawn mower blade. A lot of people use this method in order to save time but it’s also ideal if you’re looking for a way to sharpen a blade that has a lot of nicks in it.
You will need to make sure that you make light passes and maintain a consistent angle as you grind the blade.
Most people want to know what grit flap disc for sharpening lawn mower blades with an angle grinder. You need to make sure that you are using a grinding stone disc as this is the best type for grinding the metal of the lawn mower blade.
How To Sharpen Mower Blades
Now that we are familiar with the best ways to sharpen lawn mower blades, it’s time to understand how to get the job done properly.
When we talk about grit, we are talking about how abrasive the surface of the grinder or file is. Depending on the type of tool you are working on, different grit levels will be required. The lawn mower blade is no exception to this rule.
It’s a good idea to stick with a grit between 60 and 80 when it comes to working on your lawn mower blades. This falls into the category of medium coarseness so it’s ideal for removing metal as well as getting a precise cutting edge. If you use something that’s much more coarse than this, too much material may be taken away whereas something finer might not be intense enough.
When you sharpen your lawn mower blades, the most essential priority is making sure you are safe. Even when the blade is dull, it can still do some serious damage so safety gear and being careful are a no brainer!
Don’t ever be tempted to reach underneath the deck if the mower is on. Always make sure to disconnect the power before you perform any maintenance. For gas mowers, disconnect the spark plug, electric mowers should be unplugged from the mains and cordless mowers should have the batteries removed.
Once you’ve done that, you can follow this easy step by step guide to sharpening your lawn mower blade.
1. Accessing The Blade
Before you do anything else, you’re going to need to take the blade out of the mower but you can’t do this if you cannot access it. If you’re using a push mower then you’ll need to tip it over onto the side. For gas mowers, this should be done with the carburetor pointing up so that there is no chance of oil leaking inside the engine.
For riding mowers, you cannot tip the machine onto its side but you can use a jack to tilt the mower up onto the rear wheels allowing you access to the underside of the deck.
Before you do anything with the blade, take the time to note which direction it is installed. You can take a photo or mark the blade to ensure you don’t forget as you must make sure that you put it back in the same way otherwise it won’t work.
2. Removing The Blade
Now it is time to take the blade out and you’ll do this by removing the bolts that keep it in place. For this, you will need a socket wrench as this is kinder to the bolts and won’t wear them out.
When unbolting, keep the blade still by putting a piece of 2 x 4 between it and the deck. Then start turning the bolt anticlockwise. However, there are some bolts that are threaded the other way so do keep this in mind.
3. Sharpening The Blade
So, you’ve got the blade out of the lawn mower and are ready to sharpen it. You’ll need to have a vice to hold the blade in place while you work and make sure that the sharp edge is pointing up.
Many people will opt for a grinder as this is a much quicker way to sharpen the blade. However, if you’re looking for a safe option then using files is the way to go. Plus, you have much greater control so there is far less chance of over sharpening the blade.
Take a 10 inch file and use this to sharpen the edge using even downward strokes. The blade will already have an angle so make sure to keep to this and remove any nicks and bring the blade to a uniform sharpness.
When you maintain your blade regularly, you’ll find that it doesn’t take more than around 50 passes to get the job done. But of course, this will depend on how much wear the mower has been through between sharpenings.
4. Reinstalling The Blade
Now that you have a nice sharp blade, it’s time to put it back into the mowing deck. Remember to install it in the same way that you found it. There’s nothing more annoying than having to take it out, turn it around and do it all again.
Do You Sharpen Both Sides?
If you are used to sharpening kitchen knives then you will know that sometimes the blade needs to be sharpened on both sides while other times, it’s just on the one side. This can leave people wondering whether you need to sharpen both sides of the lawn mower blade.
With mower blades, you only need to sharpen one edge as the blade only turns in one direction so one side of the blade does all the work. In fact, if you were to sharpen both sides, you’d probably find that the blade was thrown off balance which would negatively affect its performance.
On top of this, sharpening both sides can affect the lifespan of the engine parts since the off balance blade will vibrate and increase wear on them.
How Sharp Should Mower Blades Be?
It would be easy to assume that the sharper the blade, the better. This is the case with some blades but not where your lawn mower is concerned. You see, it is perfectly possible to over sharpen a blade and when it is too sharp, this can make it more brittle therefore more prone to chips and nicks. This is all because the blade is much thinner when it’s so sharp.
What’s more, if the blade is super sharp, it will get dull much more quickly so you’ll only be making more work for yourself.
Most experts would suggest only sharpening to the same level as something like a butter knife. You’ll still get clean and neat cutting at speed but without the risk of damage to the blade.
Final Thoughts
Getting your lawn mower blades to just the right sharpness is super important if you want a uniform cut. However, one of the most common questions is what is the best grit for sharpening lawn mower blades?
You need to stick between 60 and 80 grit for grinding wheels. If you are using files then start with something coarse before finishing with a medium or fine file.
Always make sure to sharpen the blade safely and don’t go over the top as this can do more harm than good.
