You might think that sharpening a lawn mower blade takes a lot of skill. While years of practice will hone your technique, the basic principles of blade sharpening are fairly simple. Our DIY instructions show you how to quickly sharpen your lawn mower blades so you can save money and keep your lawn looking great.
Table of contents
- Why Sharpen Lawn Mower Blades?
- How to Decide Which Way to Sharpen Your Lawn Mower Blades
- How to Sharpen a Lawn Mower Blade Using an Angle Grinder
- How to Grind a Lawn Mower Blade Using a Bench Grinder
- Balancing Lawn Mower Blades
- Other Ways to Sharpen Lawn Mower Blades
- More Notes
Why Sharpen Lawn Mower Blades?
You might think that a blade spinning at over 180 mph or more doesn't need to be very sharp to cut grass. you are right. However, a sharp blade cuts through the grass, allowing it to grow in a healthier manner.
Why is this important? Because "chopped" grass tips can quickly turn brown, leaving your lawn looking tattered and burnt. The diagram below helps illustrate this:
For professionals, and for those who — let's be frank — like a nice lawn, having a sharp lawn mower blade is really important for a professional look. That's three times as high for a species like fescue grass that grows more or less straight out of the ground and requires frequent cutting.
We know the pros sharpen their zero-turn lawn mower blades every other day.
How to Decide Which Way to Sharpen Your Lawn Mower Blades
There are many ways to sharpen your lawn mower blades. Some of the easiest (and fastest) methods involve using a grinder. The blades don't actually need to be razor sharp — they just need to have a decisive cutting edge. It's this edge that cuts grass at high speeds instead of shredding.
Of course, grinders come in many sizes and shapes. Angle grinders, bench grinders… you name it. If you already own one of these tools, you probably have everything you need to sharpen your lawn mower blades. If not, one of our other solutions might work — so read on.
Instead of using a grinder, you can grab a hand file and get to work. A dedicated blade sharpening system exists to ensure proper angle and consistency when sharpening these heavy duty blades.
No matter which method you choose to sharpen your lawn mower blades, we'll start with the most common and work your way up.
How to Sharpen a Lawn Mower Blade Using an Angle Grinder
Grinding your lawn mower blades with a small angle grinder allows you to get the job done with minimal time investment or cost. You can get an angle grinder for very little money, and the process involves matching the angle of an existing blade edge and simply honing it.
To sharpen your lawn mower blades with an angle grinder:
- Remove the lawn mower blade and place it in a vise
- Attaching the Grinding Wheel to the Angle Grinder
- Run the angle grinder back and forth along the blade, maintaining the existing angle of the blade
- Balance the blade to ensure the same material is removed from both ends (see below)
How to Grind a Lawn Mower Blade Using a Bench Grinder
Similar to the process above, sanding your lawn mower blades is just as easy with a bench sander. Bench grinders reverse this process. Instead of moving the grinder to the blade, move the blade to the grinding wheel. Since many bench grinders include an adjustable table, you can often get excellent and consistent results with this method.
Try not to over sharpen the blade. Doing so will only result in an edge that is too fragile, more likely to dull and weaken the blade. You also want to use quick passes to sharpen your edge. Be careful not to heat the steel too much. If you do this, you may inadvertently weaken the hardening process that holds the edge of the blade.
To sharpen your lawn mower blades with a bench sander:
- Remove the lawn mower blade
- Set the angle of the grinder tool holder so that the blade angle matches the grinding wheel
- Turn on the Bench Grinder
- Move the blade side to side along the grinding wheel to keep the blade even with the holder
- Balance the blade to ensure the same material is removed from both ends (see below)
Sharpening Lawn Mower Blades Using Drilling and Sharpening Wheels
Another way to sharpen your lawn mower blades involves using a cordless drill and a special drill bit. You can find them in any number of shapes and sizes. These bits match the natural angle of the lawn mower blade.
To sharpen a lawn mower blade with a drill attachment:
- Put the lawn mower blade in the vise
- Insert the drill into the drill
- Set the drill to high speed
- Run the attachment along the sharp part of the blade to refresh the edge
One advantage of these types of sharpeners is that you can leave the blades on the mower. Depending on the type of blade and mower, you may get better results by removing the blade first. Still, it does offer a really quick way to keep your blades sharp.
Balancing Lawn Mower Blades
These methods are fairly forgiving, however, you should be careful not to miss one important step: balancing the blade periodically. After removing some of the metal on the sides of the blade and getting a nice edge, you need to make sure the blade is still balanced.
To do this, nail 16D or similar nails into the walls of your shed or shop, then hang the blade from its center point. If it stays in balance, you're done. If not, mark the heavier side with a Sharpie marker and remove some extra metal from that side by continuing to sand. Most of the time, you can keep your blade balanced by knowing how much you're doing with your grinder. Still, check the blade balance periodically to make sure you haven't drifted too far on one side or the other.
No matter which grinder method you use, periodically balance the blade to make sure it stays flat.
Other Ways to Sharpen Lawn Mower Blades
We generally do not recommend using files when sharpening lawn mower blades. The process is slow and manual and won't make your lawn better or blade life longer as a result. Instead, choose one of the grinder methods above and get to work. However, if you prefer to use a hand file – by all means, use it.
If you happen to sharpen your lawn mower blades on a regular basis — enough to warrant a quicker process — there are indeed several business models that can save you time. A newly developed tool from Noracore, the Easy Mower Blade Sharpener (EMBSX), holds particular promise. In fact, the tool won a 2019 Pro Tool Innovation Award.
This air tool drives a die grinder with mirror and camera interface, allowing you to sharpen blades on zero-turn lawn mowers without removing the blades. Using it requires some skill and skill, so it's not for everyone. You also need to be careful not to sharpen one side more than the other, or you could throw the blade out of balance.
More Notes
No matter which method you choose to sharpen your lawn mower blades, be sure to wear proper personal protective equipment (PPE) to protect your eyes, hands and ears. Sharpening a lawn mower blade is a no-brainer, and we've found it's a great entry-level task that just about anyone can do. However, accidents can be prevented by taking proper safety precautions.
Let us know your thoughts in the comments below. Do you have a preferred method of sharpening your lawn mower blades? In your experience, which method works best? We'd love to hear from you.