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How to Sharpen Lawn Mower Blades

When you mow your lawn with the dull blade of your lawnmower, your grass can turn brown due to the ragged cuts. For this reason, it is important to have sharp lawnmower blades. It can keep the grass healthy and green and the mow will also last longer.

All you have to do is to sharpen the blade to have clean cuts. In doing so, your lawn mowing time will be reduced and the grass can recover quickly. Here we shall explain to you how to sharpen the lawnmower blade safely.

Requirements –

The tools required for sharpening lawn mower blades are socket wrench or ratchet set, vise, bastard-cut mill file, and rags. The materials that you require will be work gloves and WD-40 lubricant.

When To Sharpen Your Mower Blade?

When you cut the grass, the nutrients will return to the lawn so that there will be strong and green-looking grass. For this, it is important to provide clean cuts. You can offer a clean cut with a sharp mower. However, with regular use, the lawnmower blade can become blunt and dull. It is important that you inspect the blades from time to time.

  • When there are worn-out blades, you will have to remove them and hone the edges.
  • It is advisable to sharpen the mower blade at least twice a season.
  • Some people often tend to sharpen the blades after 25 hours of use.
  • You will also have to sharpen them when the blades hit rocks which can cause dents.
  • At times you will find it difficult while mowing, where the lawn will give you hints that the blades are dull.
  • You have to look out for different signs like uneven grass height, dents or nicks, torn-looking blades, or frayed grass edges.

Removing and Cleaning Blade

To sharpen the blade, you will have to safely remove the blade from the lawnmower. It is always advisable that you disconnect the power source or battery. Always disconnect the spark plug wires. It helps to protect from any kind of shocks due to power. You can do it in the following way:

  • For better safety, you can wear protective eye gear and gloves.
  • Firstly, always drain the gas tank which will help to prevent fuel spills. You need to turn the mower on its side carefully. However, make sure that the carburetor and air filter are on the upward-facing side.
  • Use a permanent marker or a grease pencil to mark the bottom of the blade. In doing so, you will be able to install it right side up after sharpening the blade.
  • Now you will have to look out for the nuts. By using a wrench or a socket, you can easily loosen the nuts to release the mower blade. Apply more leverage if the grip is very tight. You need to clamp the blade and brace it with a piece of scrap wood.
  • If in any case the threaded shaft and nuts are stuck together, you will have to apply penetrating oil. Always allow it to sit in for a couple of hours.
  • Before sharpening, you will always have to clean the blade with a microfiber cloth or a dry rag. At times you may find the blade to be covered in grass clippings where you will have to use penetrating oil. Allow it to sit for some time and then scrub the debris with a stiff brush.

How To Sharpen Lawn Mower Blade?

To prepare for cleaning, you will have to gather the tools. You will first have to confirm if the blade is damaged or dull. Keep in mind the opposite sides of the blade have a cutting edge of up to 4 inches. To examine the blade, you will have to clamp the mower blade onto a worktable. Keep the cutting edge facing upwards. Look carefully for the signs if it requires sharpening or replacement. A replacement has to be done if the blade has cracks or if it is severely bent. If the blade is dull or chipped, you will have to sharpen it.

The lawnmower blade sharpening can be done in multiple ways. To sharpen it with the hand you will require abrasives or metal files. If you are looking to sharpen it with a machine, you will require a bench grinder, angle grinder, or blade sharpener.

While sharpening you will have to do it safely so that it will not cut your finger. If it is a razor-sharp blade, the likelihood of becoming dull is even more. It is advisable to go for replacement rather than have constant sharpening.

Sharpening by Hand

Always begin by wearing protective gloves and eye gear. You will have to protect yourself from metal shavings and sparks.

  • Use a grindstone or a file of 10 inches to sharpen the blade’s edge. You need to keep the file approximately about 45 degrees.
  • Begin by sharpening from the top side.
  • You will have to push the file in one direction without sawing back and forth.
  • While filling, you will be able to feel the file teeth. When there is no such feeling, you will have to apply a little pressure.
  • Try to reach rough spots and follow the blade edge’s angle. Do note that most blades require sharpening in less than 50 file strokes.
  • After finishing one edge, you will have to release it from the vise.
  • Repeat the process by turning it over to the other side.

Sharpening with Blade Sharpener

Here also you will have to put on gloves as well as hearing protection.

  • You will have to begin by clamping the blade into a vise.
  • Take a standard drill and insert the blade sharpener into it. The blade sharpener comes with a grinding stone that has a beveled edge. It also features a shank of 0.25-inch and a guide piece.
  • Begin by pulling the drill trigger to start it.
  • You can now place the grinder on the mower blade. To have the right sharpening angle, you must keep the flat guide against the blade rear. Also, the cutting edge must slot into the bevel.
  • By applying medium pressure, you will have to move the stone back and forth. Check the blade after every five strokes. It has to be free from any rough spots or nicks and must be very sharp.
  • Complete the edge and then turn the blade over. Begin the process and sharpen the other edge.

When you happen to use a power sharpener, never overheat the blade’s edge. If it is ho,t you can dunk it in a bucket of water.

Sharpening with Angle Grinder

To begin with, you will always have to wear safety gear like ear and eye protection and work gloves.

  • Clamp the blade by using a vise. For the angle grinder, you can use a flap disc.
  • It is advisable to align the mower blade cutting edge with the grinder’s blade.
  • You need to move the grinder slowly against the edge of the blade.
  • Try to do it on the existing edge and make sure there are no rough spots.
  • After completing one edge, you can repeat it by turning it over.

If you feel that the sharpening is complete, you can always check it. Get a piece of paper or a blade of grass and it must cut easily.

Check Blade Balance

Before you install the blade, it is important to confirm the blade balance. An unbalanced blade can lead to vibrations that can damage its components. A well-balanced blade will have smooth running. Any imbalance can even damage your mower and you will have to look for a replacement. There are even ways to check the blade balance by using a blade balancer. You can confirm it in the following way:

  • You can begin by supporting the blade like a scale and using a screwdriver. Now insert the tip of the screwdriver in the blade’s hole. You will find that the blade will balance or drop on the handle.
  • Holding the blade horizontally, you must let it go. In this process, keep in mind that it should remain level.
  • The primary sign of an unbalanced blade is that the blade drops at one side.
  • It can even happen that the depth side is heavier. You will have to remove some metal by taking off a few strokes.

Reinstall the Blade

Reinstalling the blade is a key factor in determining the overall performance. If it is under tightened, then it will make the mower hard to start. During this process, you can easily clean the bowl around the blade. Make sure that you like the area clean which is under the mower. Remove any grass clippings or mud by using a putty knife or scraper.

  • Begin by inserting the blade onto the bolt. Do note that the marked side must be upward.
  • By using a socket wrench, you can tighten the nut. It has to be secure and must be extremely tight so that the mower can start smoothly.
  • You can now connect the spark plug wire as well as the power source.
  • In the next step, you must refill the gas tank.
  • To prevent any fumes, you will have to roll the mower outside the shed or garage.
  • Finally, you can see if the mower starts smoothly.

How to Maintain Your Mower Blade?

Blade maintenance is an important thing for or perfect lawn. You will have to sharpen your blade at least twice during the mowing season. It can provide a healthy lawn and your mower will be in good shape. It does mean that you will have to keep good attention to the blades. You will have to sharpen the mower blade every time you have used it for up to 25 hours. For this, you can calculate the time you have mowed in a season. By keeping sharp blades, you don’t have to worry about getting a new one. In doing so, your blade can last longer.


We have discussed how often should you sharpen your blades. It is very important to sharpen the mower blade. Sharp blades offer clean mowing and can save you money. It can last very long when there is proper maintenance. You will have to look for any signs which can actually compromise the performance of the mower. However, you must maintain safety while sharpening the mower blade and do it carefully.

One Response

  1. Hi, I really liked the articles on sharpening lawn mower blades. But I have come up with a question. I have a lean mower with two blades.
    So when I put them back on how do they need to go back on?
    I mean like should they be placed like this – – or || or — l. Not sure how to explain it. Do the blades both face like on a clock 9 to 3 or do I place on blade at 9to3 & the other at 12to6?
    I hope you can understand what I’m trying to ask.

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