How To Sharpen Lawn Mower Blades at Home

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A lawnmower is a key equipment in lawn care to keep your turfgrass beautiful and smooth. But not one with a dull blade. Dull blades will cut grass roughly, weaken your plant with rough cuts, and leave your tuft a ragged appearance. That’s why you need to know how to sharpen lawn mower blades.

Sharpening lawn mower blades requires a little effort and skill. I believe that with my detailed guide below, even a novice can do it perfectly.

How Often Should Mower Blades Be Sharpened?

The frequency of having your lawn mower blades sharpened depends on some factors. But the general rule of thumbs for rotary mowers is you need to sharpen the blade every 20 to 25 hours of use no matter what types of lawn you own.

However, there are some external factors that will affect this guesswork. You should be ready to sharpen your lawn mower blade when it shows signs of getting dull. A ragged cutting swath with the brown area will tell you that your blade needs sharpening.

A defective lawnmower blade
A defective lawnmower blade

So, it’s recommended to sharpen your blade twice every year for the best performance of a lawnmower. The first blade sharpening task should be performed prior to the start of the mowing season. And in the middle of the season, mower blade sharpening is necessary to maintain its power.

How To Sharpen Lawn Mower Blades

Part 1: Remove the blade from your lawnmower

Detach the blade from this landscaping tool is the very first step that you should do prior to any mower repair tasks including sharpening your blade. Not only you will have more access to the blade, but it also lowers the risk of damaging the lawnmower.

You will need:

  • A separate container
  • Something to mark the blade side (spray paints or adhesive tape)
  • A wrench or ratchet
  • Some penetrating oil
  • A paint scraper or a putty knife
  • Protective gears (gloves and eye protection)
Removing a blade
Removing a blade

Now. let’s get the ball rolling:

  • The first step is to detach the ignition wire and the spark plug wire. Also, you need to disconnect the machine from any power source to prevent the mower from sudden starting.
  • Check for the gas and oil container of your lawnmower. It’s better to use up all the gas before home repair. You should pour the oil out to a container, and change the oil if necessary.
  • Now, turn your power tools on one side with its carburetor and air filter facing up. Keeping the carburetor up will prevent oil spilling; thus you will not experience smoke when restarting the machine. If you don’t know where your carburetor locates, take a look at the manual book.
  • Use a paint spray or adhesive tape to mark the facing-down side of the blade. This will help beginners avoid installing the wrong side of the mower blade.
  • Now you will need to take off the blade by loosening a bolt at the center of the blade. To make it easier, you should hold the blade while using a wrench to unscrew the bolt. If your bolt is rusted and stuck, you can use some penetration oil.
  • Use a paint scraper or a putty knife to scrape out all the curd and debris stuck in the underside of your mower. Also, take off all debris and junk sticking on your blade with a scraper.

Part 2: Sharpening the blade

There are several ways to sharpen lawnmower blades. In this writing, I will introduce to you the two most effective and simple methods to bring back a butter knife sharp blade. And remember to equip yourself with standard protective gear such as gloves, masks, and safety glasses.

Sharpening by hand


  • A vise or a sturdy clamp
  • Some piece of newspaper
  • A sharpening file

3 Steps to sharpening a blade by hand

  • Immobilize your blade with a vise and keep the edge side facing up. You can choose a suitable angle to clamp the blade and make it convenient for you to work on this blade.
  • To make cleaning after sharpening more convenient, you should lay down some newspaper under the working area. As the dust from sharpening blades is fine-grained, you might find it hard to clean the space without having newspapers.
  • Now you should take your metal file and follow the same cutting angle that the grass blade was originally sharpened. Draw the file along the edge in only one direction until you get a desired sharp edge.
Sharpening a blade with a file
Sharpening a blade with a file

If you find my guide difficult, this video will help you.

Sharpening with a machine


  • A bench grinder or a belt sander
  • A bucket of water

Guide on sharpening with a machine

  • Turn on a grinder to sharpen the blade. Then move your blade back and forth at the original angle against the grinding wheel. Pause the angle grinder for a while to check whether your blade needs more sharpness.
  • Do a similar task with a belt sander. Maintain the original angle while rubbing the edge of the blade against the sandpaper.
  • The friction when sharpening the blade will heat up the blade and make it extremely hot. To prevent overheating, you can dip the blade into the bucket. Wipe the blade with rags before continuing sharpening it.
Read more:  How To Choose The Best Corded Electric Lawn Mower
Sharpening a blade with a grinder
Sharpening a blade with a grinder

Part 3: Balancing the blade and reinstall it

The next important step you need to take is to check whether the blade is well-balanced. Mowing with an unbalanced blade will cause this outdoor power equipment to shake and damage the motor.

You can check the blades balance by slip the center holes of the blade over a nail on the wall. Then check whether the right and left part of the blade is leveled. If not, you can use a file to remove metal on the heavier side and retest it. You can also you a sharpening stone to balance the blade.

When they is ready, you can reinstall the blade. Remember to put the marked side down and snugly screw the bolt back to attach the blade to the mower deck securely. Now, plug the ignition wire in, fill the gas tank and your outdoor power machine is ready for a test run.


Now you know how to sharpen lawn mower blades at home. These methods work perfectly for my riding lawn mower, so I hope that they work for you too. It’s your turn to give them a try before the mowing season comes.


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