Lawn mower with blades. Are Lawn Mower Blades Universal (Don’t do it! )

How to Sharpen Your Lawn Mower Blade for a Cleaner Cut

Follow this easy guide to sharpening the business end of your mower and your grass will look tidier and stay healthier all season long.

Viveka Neveln is the Garden Editor at BHG and a degreed horticulturist with broad gardening expertise earned over 3 decades of practice and study. She has more than 20 years of experience writing and editing for both print and digital media.

When your lawn mower isn’t making the cut anymore, usually it’s because the blade has lost its sharp edge from use. Removing the blade and sharpening it yourself can seem intimidating if you’ve never done it before. But it’s actually a simple process, and you’ll only need two tools to do it.

Once you know how to sharpen your lawn mower blade, it’ll take you a fraction of the time it takes to mow your lawn. So, just follow this step-by-step guide to give your grass a crisp, clean cut again. Or, if you don’t want to worry about sharpening the blade, you can just remove it and bring it to a lawn mower repair service near you to take care of it.

Test Garden Tip: When grass blades have torn, ragged ends that turn brown after a mowing, chances are it’s time to give the blade some attention. Most experts recommend sharpening power mower blades once or twice a season, depending on how often you use your mower.

Step 1: Remove Blade from Mower

Disconnect the spark plug on a gas mower or unplug an electric mower (to ensure the machine won’t accidentally start while you’re working on it). Next, gently lay the mower on its side and use a wrench (27, The Home Depot) to remove the nut that attaches the blade to the motor. Then, remove the blade from the mower. To make sure you replace it the right way in the machine, mark the bottom of the blade with spray paint so you know that it should face the ground when you’re done.

Step 2: File Blade

Clean any dirt or grass clippings off the blade with a dry cloth. Stabilize the blade in a vise and use a medium file (10, The Home Depot) to smooth out imperfections along the blade edge (at the ends of mulching blades). Follow the existing angle of the blade, holding your file or sharpening tool at about a 45-degree angle. Move the file in one direction, gliding out toward the edge, much like you would sharpen a kitchen knife. However, your goal is to make the edge about as sharp as a butter knife rather than your favorite chef knife.

Step 3: Check for Balance

After you hone the cutting edge on both halves of the blade, check to see if the blade is balanced. An easy way to do this is to pound a long nail into a wall in your garage and rest the blade’s center on the nail. If the blade isn’t balanced, file a little more metal from the heavier side until it balances.

Step 4: Reassemble Mower

When the blade is correctly balanced, put the mower blade back onto the machine using a wrench. Be sure to tighten the nut securely back into place. And don’t forget to reattach the spark plugs.

Are Lawn Mower Blades Universal (Don’t do it!)

A new blade can make a huge difference to the performance of your mower and the quality of the cut. I like to change my blade every three years. But the correct blade is critically important, a mower blade tip travels at more than 200 mph. I never take a chance with a poor-fitting or damaged blade.

So, are lawn mower blades universal? Lawnmower blades are not universal, they are mower specific. A mower blade must be an exact fit and torqued to the manufacturer’s specification.

I’m a mechanic for more than twenty years and in this post, I’ll share how to identify the correct blade for your mower. I’ll also cover costly and dangerous mistakes to avoid when choosing and fitting a mower blade.

If you need video help, check out “Replacing mower blade video” in the mower repair video library. It walks you through the whole process, inspecting blade and blade boss, removing the blade, sharpening, balancing, refitting, and torquing the blade bolt to spec.

Ordering The Correct Mower Blade

Ordering the correct blade is obviously the first important step. Getting this wrong can lead to an ill-fitting and dangerous blade. Luckily, Identifying your blade is easy, there are a few ways to go about this.

Mower Make Model

Order a new blade by make and model, you’ll usually find the badge or label on the mower chassis or deck. I know for some, the label will be missing or unreadable, but not to worry, we have other ways to ID the blade.

Make and model number label

If you do have a label, inputting the make and model numbers in Amazon will likely give you a list of suitable blades. I like to use genuine parts if possible, the fit and quality are usually best. A good seller will list the part number also, which brings us to the second way to identify the correct blade.

Blade Part Number

Every mower blade has a part number stamped into the body. The numbers are unique to that part and very often just typing said number in google will offer a list of sellers. However, I know blade part numbers can be difficult to spot, years of grass clippings and corrosion, etc.

Check out the Amazon lawnmower blade link below.

Blade Sizing

The third way to order a blade is by sizing it. I’ll often have no choice but to size a blade, as customers will just walk in with blade in hand and no other details. There’s no mystery to sizing a mower blade correctly, however just before we do we, need to identify the type of blade fitted.

There are two common types of lawnmower blades. The Lift blade is also known as the 2 in 1, and the Mulching blade, also known as the 3 in 1.

Mulching is a common feature on modern mowers, it allows the operator to drop the clippings back onto the lawn instead of collecting them. Modern mulching blades aren’t a true mulching blade, they are in fact a sort of hybrid, a cross between a lift and a mulcher. You can read more about both types here “Grass catcher troubleshooting”.

The type of blade is important, briefly, a Lift blade (2 in 1) is designed to collect grass, it does a really good job at leaving a clean lawn with no trailings. The Mulching blade (3 in 1), is designed to collect grass or mulch the grass, whichever the operator prefers.

So how do you tell a Lift from a Mulcher?

The Lift blade will characteristically have large wings, and a shorter cutting leading edge. Often referred to as the 2 in 1 because it cuts and collects.

The Mulching blade will have much smaller wings and a much longer cutting leading edge. Most importantly of all, to make a mulching blade a mulching blade, the leading edge must be curved. It’s often referred to as a 3 in 1, because it cuts, collects, and mulches.

And finally, we can get to the sizing. There are three important measurements to note:

1 The overall length measured in inches – The overall length is important, too short, and your mower isn’t cutting the correct swath, too long and, well, the blade just won’t fit.

2 The diameter of the center bolt hole – The center hole, now this is a critical measurement. The center hole of the blade isn’t just the bolt hole, it’s the balanced center of the blade.

3 The blade boss shear pin locating hole distance – The shear pin hole distance is basically the distance between the center bolt hole and the shear pin locating holes. These guys must be right or the blade won’t seat on the blade boss correctly.

Mistakes to Avoid

The following are real dangers and mistakes that I see customers make every season.

• Fitting the wrong blade type – causing the mower to under perform.
• Fitting a blade with a larger center bolt hole, causing the blade to be off balance and cause excessive vibration.
• Turning the mower over on the wrong side – mower should always be tilted with air filter side facing up, check out this post “Correct way to tilt your mower”.
• Fitting the blade upside down – the blade wing tips point away from the grass. Some blades may have grass side stamped into the blade.
• Over-tightening your blade bolt – when the blade is too tight, the engine may fail if the blade hits a solid object. Check out this post “Engine kickback”.
• Turning the blade bolt the wrong way and damaging the threads. Check out this post “Blade bolt stuck”.

Wingtips point away from the grass

Removal and fitting are all covered in this video “Fitting a mower blade”. You may also find “Setting a torque wrench video useful”.

Symptoms of Wrong / Damaged / Badly Fitted Mower Blade

The following symptoms are a sign of a possible problem with the blade assembly and should be investigated for loose or damaged components. Check out blade maintenance tools here, they make the sharpening and blade replacing process almost pleasurable.

• Excessive vibration
• Constantly loosening blade bolt
• Constantly loosening mower components
• Knocking noise
• Mower not bagging grass

Related Questions

Are lawn mower blades meant to be loose? Lawnmower blades are meant to be tight. Use a torque wrench to tighten the blade bolt to the manufacturer’s specification. Overtighten a mower blade is bad also, it may cause engine damage.

Hey, I’m John, and I’m a Red Seal Qualified Service Technician with over twenty-five years experience.

I’ve worked on all types of mechanical equipment, from cars to grass machinery, and this site is where I share fluff-free hacks, tips, and insider know-how.

And the best part. it’s free!

Definitions : Reel and Rotary

A Reel Mower is a mower in which the blades spin vertically (north to south) and use a scissoring action to cut the blades of grass. A reel mower should have between three and seven blades, depending on the model type.

• Golf courses are most often cut with reel mowers which are pulled by a tractor.
• A Reel mower pushed by people does not cut very high grass as well or as easily.
• However, once the lawn is under control, the scissor-like cut of a reel mower is healthier for the lawn.

A Reel mower snips the grass, cutting each blade like a pair of scissors. It’s a precise, clean cut that makes for a healthier and more attractive lawn.

A Rotary Mower is a mower in which the blade spins horizontally (east to west) and uses a sucking and tearing action to cut the blades of grass. Rotary mowers usually have one blade which rotates very fast. The rotary mower design is simple and adapts very well to small engines. Rotary mowers can cut a wide variety of grass conditions. Rotary mowers are usually powered by gas engines or electric engines.

Over the course of a cutting season, leaving lawn clippings as you mow is equivalent to a free application of fertilizer.

Mulching (Grasscycling) means laying a blanket of organic matter over the lawn which helps to retain moisture and add nutrients. With the cutting action of a reel mower you can leave reel clippings on the lawn. A reel mower creates a fine spray of clippings that act as a mulch and decompose quickly, releasing nitrogen into the lawn. Over the course of a cutting season, that mulch is equivalent to a free application of fertilizer.

Many states (24 at this writing) and Washington, D.C., have passed laws banning the disposal of yard waste, including grass clippings in landfills. According to the Composting Council, yard trimmings are the second largest component of municipal solid waste (18 percent or 35 million tons).The Professional Lawn Care Association of America is promoting Grasscycling. This term means either composting or mulching the clippings where they are produced.

Reel Mowers

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This reel mower is specifically designed to cut low-growing, creeping grasses.

Earthwise 18 Quiet Cut Reel Mower

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The Earthwise 18-inch Quiet Cut Reel Mower features a non-contact quiet reel system for quieter and smoother operation.

Scotts 20 Classic Reel Mower

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This large reel mower cuts as wide as a traditional gas powered mower but without the harm to the environment and loud noise.

Hudson Star Classic Cut Mower Reel Mower

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Hudson Star Greensmowers have lower cutting heights than most reel mowers and will mow low enough for a putting green.

Rotary Mowers

Earthwise 20 Cordless Electric Lawn Mower

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The Earthwise 14 Corded electric mower delivers the performance of a rotary lawn mower without gas, oil or pollution.

Resources ::

PPM has enthusiatically developed an outreach page for gas mower emmissions and related research. Find:

How Fast Does a Lawn Mower Blade Spin and How To Know Speed

How fast does a lawn mower blade spin is a question most users ask if they notice something off with the speed of their lawn mower blade. Understanding a lawn mower’s blade speed is crucial because it might indicate whether a problem is occurring with the machine or whether you are using it dangerously and in violation of safety laws.

In this article, we’ll talk about what the appropriate speed rate should be, what factors can affect the speed, and ultimately, how your lawn mower blade works.

Continue reading to learn more about it and get your lawn mower blade speed at its most efficient rate.

• How Fast Does Your Lawn Mower Blade Spin?

• – Type of Lawn Mower
• – Length of the Blade
• – Height of Grass
• – Blades Are in Use (Actively Cutting Grass)
• – An Obstruction in the Blade
• – Engine Problem
• – Improper Maintenance and Repairs

• – Blade Spins Too Slow
• – Blade Spins Too Fast
• – Lawnmower Blades Operations

How Fast Does Your Lawn Mower Blade Spin?

Your lawn mower blade spins at about 3,000 revolutions per minute to cut grass effectively, slicing the grass as it moves over it. Blade tips at either end do all the cutting, regardless of whether the blade is straight or curved.

However, the speed depends on the model of the lawn mower and its blade specifications. The tip of a lawnmower blade frequently turns faster. The speed range can be between 200 and 250 miles per hour, but for safety reasons, the blade’s tip should not rotate faster than 216 miles per hour. However, there are no restrictions on the RPM of the mower.

Now, there are several factors that can affect the speed of your mower blade. Below are some of these factors:

– Type of Lawn Mower

The speed of a spinning lawn mower blade depends on whether you are using a riding lawn mower or a push lawn mower. Small mowers often have higher RPMs, but large-deck single-blade mowers typically have slightly lower RPMs.

While riding mowers operate at somewhat higher speeds of 3,200 RPM to 3,600 RPM, push mowers typically remain at or around 3,000 RPM. The majority of four-stroke lawnmowers run in the 2,800 RPM to 3,600 RPM range.

– Length of the Blade

The cutting blade’s length plays a significant role in determining speed. Longer blades often turn more slowly than shorter ones when all other variables, such as mower power, grass density, and others, are held constant.

A 19-inch blade doesn’t necessarily need to spin as swiftly as a 14-inch blade with a comparable degree of sharpness to have the same cutting quality.

– Height of Grass

Long, thick grass will typically be difficult for a lawn mower to trim; thus, it can affect the rate at which the blade spins. Maintaining the blades at their ideal pace requires matching your expectations to what your lawn mower can actually do.

– Blades Are in Use (Actively Cutting Grass)

Similarly, the blade speed differs if your mower is actively cutting grass compared to when it is not. Typically, when the mower is cutting grass, the RPM of the majority of mowers drops to approximately 3000 RPM. Some even operate at speeds below 2,500 RPM but can still produce good cuts.

When the blades are not cutting the grass, the majority of walk-behind and ride-on mowers operate at 3200 RPM to 3600 RPM.

– An Obstruction in the Blade

The blade’s ability to freely spin can be hampered by excessive grass growth and wrapped objects.

Having these obstructions in your mower deck will cause the RPM of the lawn mower blade to decrease.

– Engine Problem

The engine torque and power can also affect the rotation of a mower blade. The higher these values are, the more quickly the blade is expected to spin because greater torque will result in faster mower blades. However, regardless of how powerful the mower is, some manufacturers may purposefully make the blades spin more slowly for reasons of safety, noise, or the environment.

Engine speed can be incorrectly adjusted using the throttle cable connection. The engine RPM will rise if the cable is adjusted too much in relation to the carburetor. Additionally, the blade speed can’t be achieved if the cable adjustment is set too low.

– Improper Maintenance and Repairs

The performance of the lawn mower will decline over time if it is neglected. The mower’s performance may decline, and its blade speed will slow down if regular maintenance and repairs are neglected. If you are encountering incorrect blade speed, you may want to check the problems below that may have an impact on the speed of your lawn mower blade.

• Bad gasoline
• Blunt blades
• Damaged pulley
• Defective tension spring
• Dirty air filter
• Dirty fuel filter
• Faulty spark plug
• Loose deck or blade belt
• Obstructed fuel line

How Can You Check Your Lawn Mower Blade’s RPM?

To check your lawn mower blade’s RPM, you can look at the mower handbook — the engine and blade speed are listed there. However, if you do not have it and you want to know the RPM of your lawnmower, you only need one tool: a tachometer.

If you do not have regular access to a tachometer, you can see how the grass looks after you cut it. Slow blades shred and damage grass rather than accurately and successfully cutting it. However, if your blades are moving too quickly, you’ll waste gasoline and endanger yourself.

The blade speed of lawnmowers ranges from 2800 to 3600 RPM. Even though the range will drop by a few hundred RPM once it is actively cutting the grass, there is still a required speed to efficiently cut the grass. There are only two possible outcomes: the lawn mower blade spins too slowly or too quickly.

– Blade Spins Too Slow

If your lawn mower’s blade rotates slower than what is required, it will become less effective at mowing grass. The grass will be torn, and the cuts will be sloppy when a blade rotates at a lesser pace than it was designed to.

The results are similar to cutting grass with dull blades. A weak blade will also make it difficult for the mower to clear the grass out of the way, which will slow it down. Despite the fact that mowing slowly is preferred, a mower occasionally starts off too slowly or takes a while to start.

This can be a sign that your mower needs maintenance or that something is wrong with it. It can be attributed to a dirty air filter, a carburetor, a faulty spark plug, clogged blades, and poor-quality fuel.

– Blade Spins Too Fast

Most restrictions governing the tip speed of lawn mowers are put in place for security reasons. To ensure that a blade won’t be able to go all the way through and become a dangerous projectile even if it comes loose, lawn mower decks are put through a lot of testing throughout the design phase.

The blade tip speed formula is governed by safety regulations and capped at 216 mph. Each part of the lawn mower has a maximum operating speed that has been determined. Exceeding these limitations will result in the failure of the lawn mower.

In a situation like this, it is always advised to get your mower examined by a licensed mechanic because the issue is likely mechanical. The majority of the time, a mechanic can tell whether there is a problem by merely listening to the engine.

In the long run, hiring a pro to inspect your lawnmower is probably going to save you time and money without putting you in a lot of danger.

– Lawnmower Blades Operations

With all the details about the speed of the lawnmower blade rotation, we can briefly discuss how it works and why the speed can differ depending on many factors. Old mowers do not operate like modern mowers. In the past, the lawnmowers that were used were pushed through the yard by the user. These kinds of mowers had blades that were effectively scissors attached beneath the mower.

Most lawnmowers on the market today are rotary mowers powered by gasoline or electricity. In contrast to earlier mowers, rotary mowers slice at the grass with rotating blades rather than snipping it.

Conclusion

The speed at which the lawn mower blade spins greatly affects the efficiency of a lawn mower. Many factors can affect the speed of the mower blade, and understanding all of them will be a big help, especially if you encounter problems with your lawnmower blade’s speed.

Here is a summary of what we have discussed.

• Most rotary lawnmowers work by using fuel. These commercial mower blade rpm typically ranges from 2800 to 3600 revolutions per minute, translating to around 200 mph. According to ANSI requirements, the allowable speed that is deemed safe is only up to 216 mph.
• The blade length has a big impact on the speed at which it rotates. The shorter the lawnmower blades, the faster they can spin, and vice versa. Similarly, the height of the grass to be mowed can affect the speed at which the blade spins, as can the presence of clogging or obstructions such as damp grass.
• If the blade is freely moving, meaning it is not yet actively cutting the grass, the average speed is 3000 RPM. However, once the blade touches the grass, the speed will decrease by a few hundred RPMs. Typically, it will be at 2800 to 2500 revolutions.
• Engine problems resulting from a lack of proper maintenance can also be the reason why the lawnmower blade does not have the required speed. It can be attributed to faulty or worn-out machine parts and poor-quality fuel as well.
• You can always see the blade speed in the manual of your mower. If this is not available, you can check the actual speed by using a handheld device called a tachometer. It is used to measure the engine’s operation speed in revolutions per minute or RPM.

Now that you know the recommended, average, and allowed speed rate of your lawn mower blade’s rotation, you can include it in your maintenance checklist to keep your trusty lawn mower in tip-top shape all the time.

Sharp blades all season long will give you the cutting edge you need for a healthy, green lawn.

By Bob Vila Staff and Tony Carrick | Updated Jul 18, 2023 11:38 AM

We may earn revenue from the products available on this page and participate in affiliate programs.

At the start of growing season, part of the necessary prep every homeowner with hopes of a greener yard tacks (or should tack) onto the to-do list involves the cleaning and sharpening of lawn mower blades. If the blades are left dull, each afternoon spent mowing only rips and chews the grass. Coarsely cut grass doesn’t just look bad; it’s also more vulnerable to pests, disease, and drought. Read on for our step-by-step guide on how to care for your largest landscaping tool, and you’ll reap the benefits of a clean cut all season long.

Types of Mower Blades You Can Sharpen

If you own a walk-behind or ride-on mower, then you can remove and sharpen the blade yourself. Both types have a mowing deck that’s equipped with either one or two blades that spin horizontally around a vertical spindle. Remove each blade by loosening a single nut on the spindle. If you happen to own an old-fashioned reel mower, which uses multiple blades mounted to a cylinder, then you’ll need to take it to a lawn mower repair shop to have the blades sharpened.

Project Overview

Working Time: 1 hour Total Time: 1 hour Skill Level: Beginner Estimated Cost: 0 to 12

Before You Begin

Since this job involves working with a large blade and filing or grinding metal, taking the right safety precautions to protect your hands and eyes is key. You’ll be either filing or grinding the lawn-mower blade to sharpen it, so be sure to wear safety glasses to protect your eyes from sparks and tiny shards of metal that might become airborne as you’re working the blade. Since you’ll be using your hands to hold the blade as you sharpen it, you’ll want to wear heavy work gloves to protect your hands.

• Work gloves
• Socket wrench
• Scraper
• Vise
• Safety glasses
• Bastard-cut mill file
• See full list «
• Power drill
• Sharpening stone drill attachment
• Blade balancer

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How To Tell If Your Lawn Mower Blade Needs To Be Sharpened

How often to sharpen lawn mower blades can vary based on use and other factors, but your lawn will tell you if your mower blade is in need of a good sharpening. All you need to do is look for a few telltale signs of a poor cut.

• Ragged cut: A sharp mower blade should slice cleanly through the grass. If it’s leaving a ragged edge, then the blade is tearing grass instead of cutting it.
• Uncut grass: Look carefully at your lawn after you mow it. If there are sections that appear to be pushed down instead of actually cut, then your mower blade is too dull.
• Uneven height: The grass blades should be at consistent height after you mow the yard. If they’re not, then the mower blade isn’t sharp enough to cut cleanly through the grass.
• Nicked blade: In addition to examining your lawn, you should assess the blade itself. If there are noticeable nicks and dents on the blade’s edge, then it needs to be sharpened.

How to Sharpen Lawn Mower Blades in Less Than an Hour

The type of lawn mower blade sharpener you have in your shed or garage will dictate the best way to sharpen a mower blade. Read on to learn about how to handle this lawn-mower maintenance job using a file, power drill, or bench grinder.

Step 1: Disconnect the spark plug (on a gas mower) or battery (on an electric mower).

This is the most important step in the entire process. Gas mowers start by using centrifugal force, which the user creates by pulling the starter cord. Though very unlikely, it is possible to create that same force by turning the blade. Eliminate any chance of the engine starting by disconnecting the spark plug, which is found on the front of the engine.Those with an electric mower should make sure to either unplug it from its power source or remove the battery if it’s cordless.

Step 2: Remove the blade.

Flip the mower over, so you can access the blade. Holding one side of the blade to keep it from moving, loosen the blade’s mounting nut using your socket wrench. If the nut is on tight or you don’t feel comfortable holding the blade, use a piece of scrap lumber to hold the blade in place so you can loosen the nut.

Step 3: Clean the blade with a metal scraper.

Clean the blade with a scraper and assess its condition. If rocks, branches, and other debris have inflicted deep nicks, you’ll want to replace it. Otherwise, gather the tools you need to sharpen it manually or mechanically.

Step 4: Sharpen the lawn mower blade.

At this point, you have a few options for how to proceed with sharpening, depending on the tools you have at hand.

• How to sharpen lawn mower blades with a file: Clamp the blade horizontally in a vise and run a bastard-cut mill file along the cutting edge, using a one-way down stroke. Follow the existing angle (usually 45 degrees, but you can refer to your owner’s manual for the ideal angle) until the blade has the sharpness of a butter knife. Aim to remove an equal amount of metal from the cutting edge of both ends of the blade. Counting strokes may help you keep track.
• How to sharpen lawn mower blades with a power drill: A faster technique involves a power drill with a sharpening stone attachment. Clamp the blade—cutting side up—in a vise. Secure the sharpening stone in the drill; the stone’s plastic guide should rest against the rear of the blade to ensure the proper cutting angle. Put on safety glasses, turn on the drill, and move the stone from the center of the blade to the tip.
• How to sharpen lawn mower blades with a grinder: The fastest way to sharpen the blade is with a bench grinder. With this method, you’ll need to be careful not to oversharpen the blade or remove too much metal. Oversharpening creates a thin edge, which is easy to damage, and removing too much metal shortens the life of the blade. Hold the blade perpendicular to the rotating wheel as you move it along the cutting edge at the angle of the existing bevel. This throws sparks, so be sure to wear safety glasses. If the blade gets too hot, dip it in a bucket of water to cool it.

Step 5: Check the blade’s balance.

Check the blade’s balance before remounting it, because a lopsided blade will wobble and overtax the mower’s engine. Set a blade balancer on a flat surface and rest the blade on the balancer using the center hole. If the blade dips, use the file, sharpening stone, or grinder to remove metal from the back edge—not the cutting edge—of the heavier side toward the end of the blade.

You can also check the balance by hanging the blade on a wall from a nail through its center hole. If the blade tilts to one side, remove material from that side.

Step 6: Reinstall the blade in the lawn mower.

Reinstall the blade to the spindle under the mower using the mounting nut. Tighten the nut with a socket wrench while holding the blade with one hand. Flip the mower over and reconnect the spark-plug wire or power source, and then get to work!

Final Thoughts

If your lawn mower isn’t cutting it, then it’s probably time to give that blade a good sharpening. This process isn’t difficult if you have the right tools for the job and follow the above instructions. That said, if mower blade sharpening isn’t something you have the tools or time to do yourself, you can have a local lawn mower repair shop sharpen your blade for you for about 15 to 20. If you examine the blade and determine that it’s too worn out or damaged to be sharpened, then you’ll need to purchase a new one that’s compatible with your mower brand and model for about 20 to 25.