How to Sharpen Lawn Mower Blades for a Perfectly Manicured Yard Every Time

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Taking care of your lawn can be a favorite pastime if you are looking for a fun DIY at home.

Most people list lawn care as a priority during the summer months. And doing it yourself is an excellent way to save money that you would otherwise use to pay a professional lawnmower.

Lawnmowers need care and maintenance to work efficiently, the more reason you should get into the habit of sharpening your lawnmower now and then.

The smoother the blades, the faster and better the lawnmower will work — and the nicer your lawn will look!

Sharp edges also do not cause damage to the grass, instead trim them neatly, leaving your lawn beautiful. Lawnmower blades that are blunt may pull the grass from the roots; the frequency of sharpening your blades increases if your yard has debris.

Before you start any work on your lawn, ensure you sharpen your lawnmower using the following steps.

Note: While the instructions we are providing refer to the blades on a power lawn mower, they also apply to sharpening blades on a rotary or reel push mower. What will be different is the shape and removal process of the blades. Another option, depending upon the type of mower you have, is to purchase a reel mower sharpening kit.

Related: Turn grass clippings into nutrient rich fertilizer by making a compost bin

Let’s first cover a few things you need to know about sharpening the blades on your lawn mower — regardless of what method you decide to use.

How sharp should lawn mower blades be?

When sharpening a mower blade you are not looking for something that is razor sharp. The result you want is closer to a butter knife rather than a sharp knife with thin edges.

The main goal it to get rid of any nicks and create a smooth surface along the sides. You should be able to touch the edge of the knife without getting cut. If you go for a blade that is too sharp, it will actually get dull faster and will be more likely dull get more nicks or have the edge curl over.

What is the best angle to sharpen a lawn mower blade?

When sharpening mower blades it is important that you keep whatever tool you are using flat against the edge of the blade. As you are sharpening, you also need to watch for the angle of the tool against the blade. Preferences range anywhere from 30 to 45 degrees, but many landscaping professionals recommend an angle somewhere in the middle.

Another common mistake many people make is that they shift their strokes so that they are going over the top edge of the blade, not the sides. This actually can cause rounded edges. This is true for all sharpening methods.

Okay, now that we have those tips out of the way, let’s move on to what you need to do in order to perfectly sharpen mower blades.

Step One: Clear Your Work Area

Empty the gas tank to avoid spillage during sharpening of the blades, and once it is empty, ensure there are no flammable materials near your area of work. This is because, during sharpening, the edges usually produce sparks, and if there is anything flammable around, it may cause a fire.

Also, ensure there are no children around your working area, so the sparks or debris won’t hit them during sharpening. Make sure there are no loose objects, like your clothes or even hair that may be accidentally gripped on the turning wheel.

Step Two: Disconnect the Mower

Depending on the type of lawnmower you have, the first step is to disconnect it. Some lawnmowers are corded, while others are cordless — both need to be completely disconnected from any power source. This disconnection is to prevent accidents that may occur in case the machine powers on accidentally while you are working on it.

If you own a corded mower, of course you want to unplug it. But you also need to remove the ignition wire from the spark plug. If you have a cordless lawn mower, completely remove the battery pack.

Step Three: Examine the Blade

Before you sharpen the blade, do a physical inspection and check out for defects before you start grinding. Check out for any exposed wires on the power cord or whether they are damaged.

Also, check if the blade is chipped. Sometimes when your lawn is full of debris like small stones, they cause so much damage to the edge that you may want to entirely replace it instead of sharpening.

Step Four: Disable the Blade from the Mower

In order to sharpen your blades you need to remove them from the mower. Turn the mower to the side so that the nut or bolt securing the blade to the mower is visible. Using a wrench carefully loosen the fasteners on the blade until you can safely disentangle the mower’s blade. You will either need a ratcheting wrench that fits the size of the bolt, or you can use an adjustable wrench. A crescent wrench will also work.

Sometimes the pin may be a little rusty, therefore difficult to loosen. In this case, apply some oil and let rest for a few minutes before trying to unfasten. Ensure you note which side of the blade is facing down. You will need to bolt it back the same way you disconnected it.

Step Five: Clean the Blade

Using a bristle brush, clean off both sides of the blade to remove any debris like mud, leaves, or other particles that get stuck on the edge during mowing. You won’t be able to achieve a proper sharpening without cleaning the blade first.

Spray a little oil if the debris is not coming off quickly. The penetrating oil will make it easy for dirt to come off. Be careful not to cut yourself when cleaning the cutting edges. You will want to use a wire brush to do the cleaning.

Step Six: Sharpen the Blade — 4 Ways to Do It

Depending upon your mower, there will usually be either two or three blades coming out of a center hub. There are two cutting edges on the opposite sides of the blade which are typically about 3 or 4 inches long.

We are going to discuss four of the safest ways you can sharpen your mower blades: using a flat file, a power grinder, a whetstone or a specially designed lawn mower blade sharpener.

Method #1: Using a Hand File

To sharpen the blades using a hand file, the first thing you need to do is clamp your dull blade into a vice making sure it is secure. Now, applying pressure by hand, run the file straight along the edge of the blade. This will grind out the dullness and leave your blade sharp and shiny.

Since a blade has two cutting edges, repeat the same process on the other side of the blade to sharpen both edges. This process is a little slower since you are exerting pressure by hand, but it still does the job.

NOTE: For the best results, you need to use a file that is designed to work on metal. These are often called sharpening files or bastard cut mill files. Files designed for wood working won’t work. Not only will you not get the blades sharp, you are also likely to ruin the file.

Method #2: Using a Bench Grinder

The bench grinder is presumed to be the fastest way to sharpen a lawnmower blade. However, it is a little noisy and produces a lot of sparks; therefore, you need to have some protective gear on before you use a bench grinder. Make sure to wear coveralls, earplugs, eye wear, and also work gloves.

Run the edge of your blade against a fast spinning wheel to sharpen your blade in a few seconds. A bench grinder is also perfect for edges that are too damaged or crooked from hitting stones during mowing. This machine repairs what a hand grinding cannot.

NOTE: You could also use a hand held grinder or angle grinder with your lawn mower blade secured in a vice. DO NOT try to hold the blade in one hand and the grinder in the other. It’s extremely dangerous.

Method #3: Using a Whetstone

Also known as a sharpening stone or a honing stone, a whetstone works the same way as a bench grinder, but it is smaller and more affordable. It is an upgrade from a hand file is are commonly used for sharpening knives and axes.

You can either use a flat whetstone and manually sharpen the blade by running the edge along the stone, lightly applying pressure as you do — the same way you would do if you were sharpening a knife.

The other option is to use lawn mower sharpener blade attachment for your power drill which has a built in guide to help keep the sharpener straight and help avoid rolled edges.. Or you can use a basic whetstone attachment, but this requires a much steadier hand. Using a whetstone on a drill is much faster than doing it by hand.

To sharpen your mower blade using a drill attachment, you will again start by securing the blade in a vice. Then run the rotating whetstone along the edge of the blade. The sharpening stone will clear off the dull edges. If you are using one designed for mowers, the blade will sit nicely within the guide.

Perform 3 or 4 back and forth strokes and check to see if the cutting edge is well sharpened. If not, you can repeat the process until you achieve the desired sharpness. This process also produces sparks but not as much as the bench grinder.

Alternatively, some people like to secure the drill firmly in the vice — kind of like making a mock bench grinder. If this is your preferred method, you will be moving the blade, not the drill. Just be extra cautious your hand doesn’t slip (you are wearing protective gloves, right?).

Is it whetstone or wet stone? A bit of trivia for you…

Although people sometimes call this sharpening device a “wet stone”, this is an inaccurate name for this type of grinding stone (yup, another term!). First of all, the word “whet” means “sharpen”. So these stones are used to sharpen, or to whet something. Secondly, not all uses of whet stones are actually wet.

Depending on your task, the can also be used dry. Additionally, even with wet applications, sometimes you will need water and others you may use oil. For water usage, sometimes people call them “water stones.”

Method #3: Using a Manual Mower Blade Sharpener

When it comes to sharpening lawn mower blades, we were really impressed by Smith’s handheld mower blade sharpener. You will still need a vice to hold the blade secure, but other than that the process is simple. All you need to do is run the blade sharpener across the edge, just like you would do with a dual edge kitchen knife sharpener. And no, those won’t work for a lawnmower blade!

In our opinion, this is one of the best DIY blade sharpening methods for people with little to no experience working with tools. With it’s built-guards, the risk of hurting yourself, as long as you take the proper precautions, is minimal. It also is designed to only grind along the sides of the mower blade, eliminating the risk of dulling the actual edge. Plus, the angles are perfect!

How to use the Smith’s Mower Blade Sharpener. | Courtesy of O.G. Grewell

Bonus Method: Commercial Mower Blade Sharpeners

For commercial landscapers and homeowners with a lot of acreage who need to sharpen blades more frequently or have several mowers to maintain, you may want to consider investing in a heavy duty sharpener designed specifically for mower and mulcher blades.

At minimum, you can expect to spend about $200 for one of these. If you are looking for a good side business sharpening lawn mower blades, this would also be a good investment.

Using these is beyond the scope of this article, but if you’re interested in a commercial mower blade sharpener, we suggest checking out what All American Sharpener offers.

Video Tutorial: How to Sharpen a Mower Blade

This Old House contractor Roger Cook demonstrates ways to sharpen lawn mower blades.

Step Seven: Reassemble the Blade

Once the blade is sharp to your satisfaction, put it back in its original position into the mower. Please note that when you place it back anyhow, the mower may wobble and not work correctly.

Once you fix it, using a wrench, gently fasten the bolts to secure the blade. Also, refill the gas tank and set back the battery pack for a cordless mower and restore the ignition wire for a corded mower and go for a test run to see if the sharpened blades work correctly.

Using a well-sharpened lawnmower blade gives you a beautifully manicured lawn. Lawn care becomes more comfortable with a sharpened edge. Do not forget to clean off your work area afterward.

Sharpen your blades every two weeks if you are a professional mower and every six months if you do your lawn mowing. Also, if there are visible stones and other objects on your lawn, you could pick them up by hand before you start mowing to prevent your blades from becoming dull faster.