Lawn mower handle nut. How to Sharpen Lawn Mower Blades

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

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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.

Lawn Mower Parts

Search and shop all the parts you need for your riding lawn equipment and Gator UTV including lawn mower blades, filters, belts, spark plugs, oil, and home maintenance kits.

Find Parts

Search part numbers and John Deere parts diagrams to identify exactly what you need to keep your equipment running smoothly.

Quick Reference Guides

As a John Deere owner, when it’s time to maintain, service or repair your equipment we have easy-to-use information sheets that keep your John Deere equipment running well.

Home Maintenance Kits

Feel confident in tuning up your lawn mower or garden equipment this season with our Home Maintenance Kits. Easily find the right product so you can DIY and save!

Looking for your Serial Number?

Finding your lawn mower’s model number and serial number is as easy as locating the identification tag on your machine. As seen in the example, the model number will be displayed below the MODEL heading (Example: Z235), and the serial number will be underlined on the top-right corner of the tag (Example: 130002).

If you’re looking for the engine number, that can be found directly on the engine itself.

Home and Garden, eat your heart out.

Get the latest on how to care for and enjoy your yard and garden. The articles and videos are informative and the ideas are amazing.

MowerPlus Mobile App

MowerPlus is the app you need to keep your John Deere riding lawn mower running well and your lawn looking great this season. The app tracks and records yard tasks and serves as a one-stop shop for seasonal care tips and maintenance activities. Know your mower and know how you mow with John Deere’s MowerPlus app.

The Right Part. The Right Price.

At John Deere, you get the value of choice for your maintenance and replacement parts for all makes and ages of machines – at any budget.

Genuine Parts

Genuine John Deere Belts Blades are your best choice for your newer machines.

Alternative Parts

Alternative Parts are an economical solution for your John Deere equipment.

The John Deere Easy Change™ 30-Second Oil Change System

Never drain engine oil again.

We’ve changed the oil change. Revolutionized it really. See how fast and easy changing your oil can now be on 100 Series Riding Lawn Tractors with the John Deere Easy Change™ 30-Second Oil Change System. Only from John Deere. Included on the E120, E130, E150, E160, E170, and E180 models.

Step One. Take it off.

Lift the hood. Make sure the engine is cool, then, twist to remove. It’s that simple.

Step Two. Twist and lock.

Grab the new Easy Change™ Canister, twist and lock into place. Make sure the arrow on your Filter System aligns with the arrow on your engine.

Step three. Done.

Close the hood and mow. John Deere recommends the Easy Change™ 30-second Oil Change System every 50 hours or at the end of your mowing season. Don’t drain engine oil ever again.

Draining engine oil is so 2017.

The engine modifications and new technologies are in. The re-envisioned oil filter with a media designed to resist breaking down in oil over time is here. The thousands of hours of testing are done. The end result is an all-in-one, oil and oil filter system like no other. The first of its kind. And thanks to the new John Deere Easy Change™ 30-Second Oil Change System (“System”), you’ll never have to drain the oil from 100 Series Riding Lawn Tractors again.

Here’s why: The new System captures contaminants and recharges your engine with nearly a quart (0.8qt) (0.76 l) of new oil. In fact, this System increases the amount of oil in the engine by nearly 40%. 2 Your engine likes that.

What do you mean, I will never have to drain oil from my engine again? How is that possible? The answer is simple. We have developed a better filtration system and filter design for our 100 Series Riding Lawn Tractors 1. This fully synthetic filter media has greater surface area which increases its capacity to hold harmful contaminants. What’s more, the filter media is designed to resist breaking down in oil over time. Which means you’ll get a cooler running engine. And a cooler running engine and better filtering helps increase engine oil life. John Deere’s recommended oil service for 100 Series Riding Lawn Tractors 1. is to change the System every 50 hours or once a season, whichever comes first. Remember, the System replaces a portion of your engine oil. And that’s plenty.

The System uses John Deere Turf-Gard™ Oil. Using John Deere Turf-Gard™ Oil ensures you are using the exact oil specified by John Deere engineers.

Testing. Testing. Testing. Thanks to thousands of hours of rigorous and extensive testing, you can feel confident your engine will run for years to come.

1 The John Deere Easy Change™ 30-Second Oil Change System is available on E120, E130, E150, E160, E170 and E180 Lawn Tractors today.

2 Compared to similar V-Twin engine models that do not have the John Deere Easy Change™ 30-Second Oil Change System. That includes equivalent Deere 2017 models and 2018 models without the System.

Frequently Asked Questions:

What is new with John Deere Riding Lawn Equipment?

We are excited about the exclusive John Deere Easy Change™ 30 second oil change system. Exclusive to John Deere and only available on certain models of the new 100 Series Lawn Tractors. These tractors are designed for ease of use for both operation and maintenance. The John Deere Easy Change™ System (“Easy Change”) allows the user to easily complete the recommended engine oil and filter maintenance in 30 seconds.

What is this new oil change system?

We changed the oil change. The all-in-one oil and oil filter system gives the owner the ability to change a portion of the oil and the filter in less than 30 seconds.

What happens to the rest of the oil in the engine when the Easy Change system is replaced?

The Easy Change system replaces.8 quart of oil. The remaining oil in the engine is refreshed by the charge of new oil included in the replacement Easy Change system. Combined with 40% more engine oil capacity, improved filtration and cooler running temperatures which help extend oil life, it is no longer necessary to remove and dispose of all the oil in your engine during service.

What makes the Easy Change system unique from other filters?

It is not just a filter. It is a newly developed technology system that allows a new “filter” to come already charged with oil and allows you to remove an existing filter and the contaminants inside without tools and without making a mess. Beyond the filter, technology within the canister and on your engine makes this possible.

Models with the Easy Change oil system use a fully synthetic filter that has more capacity to trap and hold contaminants. The larger surface area of the Easy Change canister acts like a radiator helping the oil to stay cool.

Does the Easy Change system somehow decrease the life of the engine?

The John Deere 100 Series lawn tractor models, with and without Easy Change, are specified for the same lifetime and are rigorously tested to the same standards to ensure the life of the tractor meets expectations.

Can I add the Easy change system to an existing tractor?

Because this system also requires unique features within the engine, the Easy Change system cannot be added to an engine that was not equipped with it at the factory.

Can I change all the oil if I choose to?

You could if you wanted to. There is an oil drain plug. It is not required for maintenance.

How often do I need to change the Easy Change canister?

Every 50 hours or once a year. The 100 Series Lawn Tractors with and without the Easy Change system have the same maintenance schedule.

What type of oil is recommended?

We recommend only John Deere Turf-Gard™ 10W30 Oil. The Easy Change canister comes pre-filled with John Deere Turf-Gard™ 10W30 oil.

How do I recycle the old oil?

Many local government recycling programs, authorized retailers, auto repair stations, and auto parts stores will puncture and recycle used oil filters and oil.

Do I ever need to add oil?

Yes. Consistent with our service recommendations for this product, you should check oil level daily and add oil if required.