Do you have a new mower or new mower blades? It’s a common enough question—whether to sharpen your new lawn mower blades or not? Well, in this article we’ll give you the answer.

As well as discussing your new mower blades, we’ll also look at how to sharpen old blades, how often you should sharpen them, how often you should replace them and what you can do to reduce damage.

Should you sharpen your new mower blades? Well, no. You won’t need to. Blades on a new mower, or just new blades, come sharp and ready to mow straight from the factory. So, there is no need to spend time sharpening them up before you start your mowing.

Let’s get down to business, and dive into all things bladed!

Do Lawn Mower Blades Need Sharpened?

Before we go any further, we should just address the basic question first. Do we need to sharpen the blades at all?

And the answer is yes. A dull mower blade is actually bad for your mower and your lawn. So, keeping them sharp will mean a healthier lawn and a longer lasting mower. With a dull blade, it kind of tears at the grass rather than cutting it. This damages the grass tips, and they can turn pale. The damaged tips make the grass more vulnerable to disease.

male sharpening lawn mower blade
Keeping your lawn mower’s blade sharp means a healthier lawn.

A dull blade can also increase the frequency of your mower getting clogged and adding stress on the mower engine. And if your mower has a mulching function, it won’t work as well with a dull blade.

Sharpening Frequency

A good rule of thumb is to sharpen your mower blades at the start of the season (or just before you put your mower away for the winter). And then, depending on the size of your lawn and how often you mow, you might want to check your blades halfway through the season.

If you are wondering how to tell if your blades need sharpening, the easiest way is to look at your newly cut grass. If the tips of the grass are cut cleanly your ok. But if they are ragged, and look like they’ve been torn, it’s time to sharpen the blades.

How to Keep Your Blades Sharper

As we mentioned above, you will need to sharpen your blades regularly to keep your mower and your lawn healthy. But no one wants to spend time sharpening their mower blades if they don’t have to!

There are two main things you can do to increase the sharpening maintenance interval.

The first is clear your lawn of stones and sticks. Apart from general wear, obstacles on your lawn are the primary reason for your mower blades losing their edge. Stones also cause knicks and dents in your blade, and these will tear at the grass. Dents are also harder to get out of the blade. Avoid these issues by removing things from your lawn that can damage the blades.

The second thing is less obvious but related to the first: Try not to have your mower deck set too low. If your mower is on its lowest setting, the blades will hit a lot more obstacles. If you have your mower blades set higher, they will simply ride over the obstructions. Also, leaving a little length on your grass is actually much healthier for your lawn.

How to Sharpen Lawn Mower Blades

It is fairly straightforward to sharpen your mower blade yourself. But there are a few things you should keep in mind. The first is: you will need a torque wrench if you take the blade off the mower. The second is: you should really use a balancing tool to make sure the blade is balanced properly when you’ve finished. And the third is: sharpening is a lot easier with a mower blade sharpener that fits on a drill.

It is perfectly possible to sharpen your blade while it’s still attached to the mower, but you’ll get better results if you take it off first. And you can’t balance it if it’s still attached.

Step 1 – Safety

First, make your mower safe. Disconnect the spark plug wire so that the blades can’t accidentally turn. And remember to wear gloves. Just because the blade isn’t sharp doesn’t mean there aren’t edges and dents that could cut. Also, make sure you wear eye and ear protection while you’re sharpening.

Step 2 – Remove the blade

Unscrew the blade bolt. If it’s been a while (or never), since you took the blade bolt off, it can be quite tough to remove. Try lubricant like WD40 or use extra leverage and jam the blade with a wooden block to stop it from turning.

Step 3 – Sharpen

With the blade off the mower, inspect it for damage and then go ahead and sharpen it. It’s best with a drill mounted sharpener designed for the job because it helps to get the right angle. But you can use a wheel grinder or even a file if the blade isn’t too bad. Make sure to go gently, don’t take off too much at a time and check the balance as you go.

It really is important to make sure the blade is balanced. This avoids excess engine wear, vibration and noise. If you don’t have a balancing tool, all you need is a nail in the side of your workbench. Hang the blade from its center on the nail and if it doesn’t hang level, take a little off the heavier side.

Remember, a mower blade doesn’t need to be knife sharp, just smooth and beveled.

Step 4- Attach the blade

This is where you’ll need your torque wrench. It’s important that you only tighten the blade to the correct torque. Check the manual for your mower and find the right tension. If you don’t have the manual, the internet is good at throwing up digital versions and if all else fails ask on a gardening forum.

The reason you should only tighten to the specified tension is that if you over tighten, you could damage or completely ruin your engine. The blade is tightened onto a boss, which is again attached to the crankshaft of the engine. It is designed so that if the blade hits an obstacle, it will slip on the boss protecting the crank shaft from damage. Over tightening means the blade might not slip on the boss and you can damage the crankshaft.

How often should I replace blades?

Another question people often wonder is how often they should change mower blades. The answer really depends on how much use and how hard that use is. If you have a large stony lawn, you’ll need to replace the blades much more often than if you have a small, completely obstacle free lawn.

male checking lawn mower blades
If your lawn mower blade has dents and damages, its time to replace it.

But in general terms, you should probably look to replace the blades once every 3-5 seasons. If the edge has completely gone or there are lots of dents and damage, then you will have to replace it. Inspect it once or twice a season to check. New blades are reasonably cheap, so there is no point skimping.


So that’s it. Now, you have all you need to keep your mower blades in optimum condition. We’ve shown that new blades don’t need sharpening, talked about how to reduce blade wear, how to sharpen your blades and how often you should sharpen and replace them.

With this article, we’ve given you all the information you need to keep slicing though that grass year on year. Now it’s time to check your mower and get sharpening. Happy mowing!