Lawn Mower Blade Sharpeners: How to Use Them and What to Buy

Sharpening your lawn mower blade is crucial to maintaining a proper lawn. How do you do it?

Lawn Mower Blade Sharpeners: How to Use Them and What to Buy

You are probably either getting ready to store your lawnmower for the winter or getting ready to take it out in the spring. While these two actions appear to be diametrically opposed on the surface, they do share one important common denominator: you’ll need to perform some maintenance on your lawn mower to prepare it for both occasions.

Sharpening your lawn mower blades is one of the most important maintenance practices. It’s one of those things you can’t avoid if you don’t want to face serious consequences that will affect both your lawn and your mower.

So, while you can choose when to sharpen lawn mower blades, it cannot be left undone.

And if you’re wondering why this is so important to take care of before starting your engine and heading to work, this article will help. We’ll also provide you with step-by-step instructions if you want to sharpen your lawn mower blade yourself. If you’d rather buy a sharpener that does all the work for you, this article concludes with a mini buyer’s guide and our recommendations.

So, let’s get started so we can get you back out there working in your lawn kingdom.

Why You Must Sharpen Your Lawn Mower Blades 

It’s not uncommon for people to forget to sharpen the cutting edge of their lawn mower blade before cutting their grass. I suppose out of sight, out of mind.

However, mowing with dull blades can damage not only your grass but also your lawn mower. Let’s take a look at everything that can go wrong if you don’t sharpen your machine’s blades.

How Dull Blades Damage Your Grass

Here are some of the consequences of believing that you don’t need to sharpen your blades.


Discoloration of otherwise healthy grass is one of the most common side effects of “cutting” it with blunt edged blades. It occurs when dulled blades tear the grass instead of cutting it.

When that dull edge rips the grass, the ends of the blades are shredded to mush. This allows vascular tissues known as xylems to open. The xylems are in charge of transporting water from the roots to the tips.

Moisture evaporates exponentially from the injured area of the grass plant when the xylems are exposed and damaged.

And as moisture escapes from its tattered xylems, the grass will quickly dry out. Bright green, healthy blades will give way to sickly, yellow ones as the chlorophyll that gives the plant its green color escapes through the torn edges. This not only ruins the aesthetic you’ve worked so hard to achieve, but it also damages the physical structure of the grass and jeopardizes the overall health of your lawn.

Some spots and discolorations in the lawn grass

Increased Susceptibility to Disease and Infection

You are well aware that dull lawn mower blades do not cut the grass. Instead, the force of your lawn mower’s whirling blades folds the grass blades over what was once its cutting edge. This causes the plant to rip apart, similar to a 30-pound fish snapping an angler’s 15-pound line.

This will harm the grass and cause open wounds in various parts of the plant. Those wounds are an open invitation to any bacteria, virus, or fungus that happens to be nearby. Worse, if you mow your entire yard with dull blades, the wounds that result can be infected by a variety of microbes at the same time.

A lawn shorn with blunt blades can suffer from a plethora of illnesses and ailments. Identifying which ones have made themselves at home on and in your damaged grass is not always easy.

Even if you do manage to correctly diagnose every problem, you’ll still need to devise a treatment plan. A strategy for curing your sick lawn without destroying anything other than the microbes that make it sick. And that can be a tall order to fill as well.

You’ll Have the Ugliest Yard in the Neighborhood

Even if you are fortunate enough to avoid all of the aforementioned maladies, those blades will almost certainly cause you to ruin a significant portion of the curb appeal you have toiled and troubled yourself over for hours on end.

You can kiss your lawn’s beautifully uniform texture goodbye because the grass is being ripped unceremoniously from different areas and heights on the individual blades. Even if it only detracts from your lawn’s aesthetic, I believe most of you would agree that achieving your desired aesthetic is one of the most important reasons you take care of your lawn in the first place.

After all, you work too hard out there in the scorching sun for it to be an eyesore. Unfortunately, mowing with dull blades cannot be remedied quickly by applying more fertilizer. You must allow the grass to grow well beyond the recommended mowing height. This ensures that you can regain the level and even texture that you strive for.
Increased Susceptibility to Environmental Stresses

Those blades wound up shredding your grass like cheese on a pizza. And this dramatically decreases your turf’s tolerance to stress conditions like heat or drought or low soil fertility. Then, once the stress has set in, it takes your lawn longer than usual to recover from it. 

Negating to sharpen your blades will also make your yard more prone to a pest invasion too.

A red lawnmower used in the lawn

Problems That Dull Blades Can Cause Your Lawn Mower

A dull lawnmower blade can damage any facet or feature that it comes into contact with. This includes the machine to which your lawnmower blade is attached.

Here are a few examples of how it can harm your tractor or walk-behind.

Increase Wear and Tear on Mechanical Components

Blades with blunt edges must work harder than they would normally. This added strain can cause the lawn mower’s engine to overheat, burn out the oil, or even die.

The engine-driven belts that turn the blades are also under increased strain. This causes them to stretch and may jeopardize their structural integrity. Both of these factors increase the likelihood of the belts snapping.

These are just a few of the issues that will cost you time and money. Repairs, mowing that takes longer, and having to replace worn-out parts before their time all add up.

The sum of these strains can shorten the life of your lawn mower. A lawn mower is a machine that should pay for itself many times over with the work it does.

However, failing to perform the necessary maintenance procedures will result in your tractor being put out to pasture before its time. Then you’re forced to spend more money on another lawn mower or hire a professional lawn care company, which will end up taking a fortune from you bit by bit.

And to think, all of this could have been avoided by simply going down to the lawn and garden center and paying the $7 for someone to resurface those cutting surfaces.

Increases the Cost of Running the Lawnmower

Those blades will make every part of your lawn mower work harder than usual. This increased power requirement will also cause the gas and oil to drain faster than usual.

As a result of using more gas and oil, the air and oil filters will be depleted faster.

You’ll cause more wear on the tires, transmission, and ignition switch, not to mention expending a lot more energy. Especially if you’re the unfortunate soul who needs to sharpen the blades on a push-style lawnmower.

By ignoring this simple fix, you may end up spending far more money on your lawn mower than you intended. Instead, it will feel like you purchased a boat.

red lawnmower to be used in the garden

How to Sharpen Mower Blades: A Step By Step Guide

There are several ways to sharpen the blade of your machine to a razor’s edge, just as there are several ways to skin a cat.

The blades can be filed by hand. The abrasive discs could be used on a bench grinder, side grinder, or angle grinder. A rotary tool, such as a drill with a sharpening attachment, can also be used.

Personally, I believe that the best way to sharpen a lawn mower blade without using a fancy power tool is to grab a screw drill (not an impact drill) and find a sharpening stone attachment designed to bring a larger cutting edge back to life.

I wouldn’t recommend completing this task without removing the blade or blades from under the mower deck. Attempting to sharpen the blade while it is still attached to the deck is inefficient for a variety of reasons.

When you take the blade out of the deck, you can inspect the entire cutting surface. You can position the blade however you want. And, once you’ve finished sharpening your lawnmower blades, you can evaluate every aspect of your work from a variety of perspectives. These benefits ensure that the lawn mower blade is completely and precisely sharpened.

1. Prepare the Engine

Remove the plugs and disconnect the spark plug wires. This will prevent unintentional engine ignition from occurring.

You should also drain the gas from any lawn mower whose tank you cannot reach to access the deck well and blade. This will prevent you from becoming soaked in petroleum.

2. Loosen the Lawn Mower Blade

You should be able to jack or lift your riding lawn mower so that you can access the mower blades while it is upright. To access the retention bolt that secures the mower blade to the deck on walk-behind mowers, drain the gas as directed and lay it on its side.

Loosening that retention bolt will necessitate a significant amount of torque from your socket wrench. Wedge a block of wood between the deck and the blade to prevent it from turning on its axis.

Loosen the retention bolt in the center of the lawn mower blades with the socket wrench. Because the bolt has been exposed to the elements, it is likely to be rusted and difficult to turn. This is easily remedied by spraying the affected area with a lubricant such as WD-40 or Liquid Wrench. Allow the lube to soak into the area for a few minutes before trying again.

If you still have problems with the bolt, find a metal pipe that is 4 to 6 inches longer than the handle of your socket wrench. The pipe should be large enough to accommodate the wrench’s handle. This will provide you with significantly more torque and leverage, allowing you to easily turn the bolt.

A person brush cleaning the lawnmower

3. Detach the Blades

Take a picture of how the blades are positioned before removing them from the mower’s deck.

The image is provided for your convenience because it is a common mistake for people to put their blade on backward because it appears identical on both ends.

Once you’ve saved an image for posterity, remove the blades from the deck and place them on a level surface with an edge, such as a workbench.

A detached sharp blade from a lawn mower

4. Clean the Lawn Mower Blade and the Well of the Deck

Now that the mower blade has been removed, you can access areas of the deck that were previously inaccessible due to the blades. There will be varying degrees of a thick and gummy caked-on layer of dirt, leaves, mud, and other debris from your lawn depending on how long it has been since you removed the blades.

Remove as much debris as you can with a putty knife or a painter’s knife. You won’t be able to clean these areas again until the blades come off, so be thorough.

After you’ve cleared out the organic debris in the deck’s well, pay attention to the mower blade on the work surface. Spray the lubricant you used to loosen the retention bolt over the entire surface area of both sides of the blade. Allow the lubricant to absorb into any material that has become stuck to the blade before removing it with a stiff-bristled cleaning brush.

5. Position the Lawn Mower Blade for Sharpening

Lawnmower blades have a cutting surface on opposing sides of the blade.
The cutting surface does not run the length of the blade bar, which is a common misconception. In fact, only 6 inches of the blade bar’s end is dedicated to the cutting surface. It’s usually only 3 or 4 inches long.
With the cutting surface of the mower blade facing up, clamp it to your work surface with a vice. This will prevent the blade from shifting while sharpening. This is critical because it can help prevent blade and person damage.

6. Sharpening Lawn Mower Blades

Your drill-powered sharpening stone is made up of a round, roughened stone, a flat sharpening guide that serves as a safety guard, and a 14-inch steel shank.

The abrasive stone has a beveled surface that grinds those few inches of cutting surface to the razor sharp angle required to cut your grass smoothly. Attach the grinding stone to your drill securely. Before pulling the trigger, make sure you’ve put on the proper PPE, such as gloves and safety glasses.

Wearing your PPE, depress the trigger of your drill completely to its hllt to run at maximum RPMs. Insert the sharpened cutting edge into the rotating sharpener. While doing so, make sure the stone’s beveled edge is facing the dulled edge of the lawn mower blade. The flat guide and safety guard should be placed against the blade’s backside.

Now that you’re in position, slowly move your cutting stone over the surface of the blade’s edge. Apply enough pressure to the two surfaces to ensure solid contact and friction.

Pull the stone from the blade after 4 or 5 passes and inspect the edge. Make additional passes with the lawn mower sharpening tool if necessary until you’ve achieved that perfectly tapered angle. Also, take the time to smooth out any chips or other minor flaws in the blade.

After sharpening the blade on one end of the blade bar, sharpen the blade on the opposite end. Clamp the vice to the blade bar in the same way you did with the first edge. Make sure the cutting surface of the blade is facing the beveled stone of the sharpening tool, and keep sharpening until those dull cutting surfaces have transformed into razor-sharp blades.

Sharpening the blades of a lawn mower

7. Once You Sharpen the Blades, You Need to Balance Them 

Now that your lawn mower blade has knife-like edges on both cutting surfaces, you must ensure that the weight is distributed evenly along the blade bar. This is an important step because these blades rely on centrifugal force to rotate in the deck. If one side of the blade has more weight than the other, the blades will wobble and cut unevenly.

No two cutting surfaces will ever be worn down in the same way. In that way, they’re similar to snowflakes. As a result, you may end up grinding much more of one cutting surface than the other. Don’t be discouraged if you don’t get it right the first time. Achieving this balance is critical to the proper operation and performance of your lawn mower.

An unbalanced blade not only adds stress and strain to the mower’s frame, but it also makes it unstable and shimmy when turning. This rattling may eventually cause the retention bolt to loosen, causing the blade to be ejected from beneath the lawn mower deck. Needless to say, this is a terrifying prospect that could cause serious harm to the lawn mower as well as any person or pet who happens to be in its path.

To avoid this disaster, run a simple test to ensure the blade is properly balanced. To complete this test, you’ll need a strong nail that isn’t completely driven into the wall. Insert the nail through the hole in the center of the blade for the retention bolt. Remove your hands and position the blade bar parallel to the floor.

If the blade does not move, you have done an excellent job and the blade is properly balanced. If it does move, the side that is closest to the ground is your heavier side. It is critical that you take your time and be patient with the task at this point. You don’t want to be going back and forth from end to end on the blade bar trying to get it just right.

So, check the balance of your sharpening stone after a couple of passes. It will not be necessary to grind a large chunk of metal away from the cutting surface. The weight will most likely be off by a few tenths of a gram. So exercise caution and avoid becoming overzealous when attempting to balance your blade.

If you want to balance your blade with greater precision, you can use a blade balancer, which is a multi-tiered cone-shaped metal instrument designed specifically for that purpose.

Place the instrument on a level surface and rest the blade so that the top of the balancer’s cone is visible through the retention bolt hole. Your blade is balanced if it comes to rest evenly with the entire inner circumference of the retention bolt channel flush all the way around the cone.
If you discover that your blade is tilting to one side, just like the nail in the wall, that is the side of the blade that must be corrected. Replace the balancer after grinding down the heavier side of your blade.

Repeat until your blade is still and parallel to the level surface on which the balancer is resting.

8. Reattach Your Sharp Lawn Mower Blades

You’ve done everything except put it all back together. This is where you’ll refer to the mental or physical snapshot you took earlier. Return the blade in the exact orientation and position shown in the image.

Once the blade is properly positioned, replace the retention bolt and tighten the bolt to secure the blade to the lawn mower deck.

The lawn mower can then be restored to working order by reconnecting the spark plugs to the engine and reattaching their cables. Once your lawn mower is flat on the ground and upright, fill the tank with gas and test your newly honed cutting surfaces.

A dull blade of of lawn mower

Recommendations for Lawn Mower Blade Sharpeners

There are several fantastic options on the market if you want to increase the efficiency and power of your blade sharpener while also making it easier to use.

There are three things to consider before purchasing a lawn mower blade sharpener.

1. Manual or Electric

There are manual and electronic blade sharpeners available in a variety of shapes and sizes. Manual blade sharpeners are less expensive but require more effort to operate. Electric models, on the other hand, are more expensive but much easier to use.

2. Blade Compatability

Lawn mower blades vary in size and length of cutting surface, as well as optimal sharpening angle. You must select a model that sharpens blades based on the size of your mower blade’s cutting surface as well as the degree of angle at which it must be sharpened.

3. Dependability and Durability

Sharpening lawn mower blades is not a tender or sensitive activity. It is loud, aggressive, and industrial. So, it’s good to know that it won’t let you down as you put your model through its paces over and over again. Grinding and sharpening metal is a task that can put some genuine wear and tear on your lawn mower blade sharpener. You want to know it will stand the test of time.

Products that I recommend

Oregon 88-023 Professional Lawn Mower Blade Grinder

Oregon is a semi-popular brand known for producing high-quality power tools. They simply do not receive as much attention as the big names like DeWalt, Ryobi, Mikita, and so on. Nonetheless, they make this 1/2-horsepower motor sharpen blades better than any of those well-known brand names.

This model can run at 1750 RPMs without missing a beat. It can sharpen blades with cutting surfaces as long as six inches long and as short as three inches. It provides the user with secure positioning for maximum control. Its height is also adjustable.

There are dual blade mower systems available that have blades that spin in opposite directions and cut in different ways. This model has a reverse switch that reverses the direction the grinding wheel turns. This enables it to sharpen the various orientations of the cutting surfaces on a dual-blade lawnmower.

While this is by far the most expensive model on this list, its long-lasting head and sturdy construction will provide you with razor-sharp mower blades for a long time. This blade sharpener is in our machine shop at my family’s lawn maintenance company. We’ve had to replace the grinding mechanism on occasion, but it’s never given us any trouble in the 7 years we’ve had it.

Oregon 88-023 Professional Lawn Mower Blade Grinder

Sharpal 103N Lawn Mower Blade Sharpener

This Sharpal sharpener, like all others in the Sharpal line, can edge blades with one or two bevels. The sharpening mechanism is made up of five different parts that all work together to provide you with pristine, acute cutting surfaces. It has three distinct slots for sharpening blades of varying angles.

It is rigorously tested on the factory floor and will continue to tick for a long time. It comes with a three-year factory warranty on parts and labor, as well as replacement if necessary.

Sharpal’s quality at this low price is by far the best value for money.

Sharpal 103N Lawn Mower Blade Sharpener

Work Sharp Knife and Tool Sharpener

Work Sharp sharpeners have received some of the highest ratings from customers who purchased the machine. There is nothing like word of mouth. Despite the fact that this model is designed primarily for sharpening knives and cutlery, it can handle the larger edges of a lawn mower blade with relative ease and efficiency.

This is possible because it comes with three belts with varying grit counts. The 80 grit belt is for coarse sharpening, the 220 grit belt is for moderate friction, and the 6000 grit belt is for more delicate finishing jobs. Its large handle makes it easy to control and adds to tool shop safety.

This tool sharpens blades with 40° and 50° angles. This blade sharpener is a powerful tool that is well-made and reasonably priced. It is backed by a one-year warranty.

Work Sharp Knife and Tool Sharpener

5000 Sharpener by All American

I believe it is critical to include a blade sharpening tool that does not have its own electric grinding mechanism. To sharpen your blades, you attach a separate grinding wheel to its frame.

The 500 Sharpener can sharpen standard blades as well as mulching blades. Its one-of-a-kind design includes an articulating arm to which the grinder is attached, as well as a vice head to secure the lawnmower blade in place. This arm securely holds the grinder and ensures that your blade is ground to the proper angle.

This model is light and portable, and it comes with a cordless grinder. The cordless feature and easy-to-carry design allow you to sharpen blades in areas where there is no power source. It enables simultaneous blade sharpening. It has an adapter pin that allows it to accept different-sized blades.

The disadvantages are that it can only sharpen blades with a 30° angle and that it is quite expensive. However, the money is well spent because you are purchasing a machine with no electric components. This significantly reduces the likelihood that it will need to be repaired.

All American 5000 sharpener
Jeffrey Douglas
Jeffrey Douglas own a landscaping company and has been in the business for over 20 years. He loves all things related to lawns or gardens and believes that proper maintenance is the key to preventing problems in the first place.
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