How To Sharpen A Lawn Mower Blade

lawn mower blade splash

Sharpening a lawn mower blade is important to keep your lawn healthy and green. A sharp blade will cut the grass blades instead of tearing the grass blades. A dull blade will tear the grass blades which results in silver or brown grass blades, this makes your lawn look brown or silver. Torn grass ends also make the lawn more susceptible to disease. This article teaches you how to sharpen and balance your lawn mower blade.

When the blade is sharp it cuts the grass more times before it gets thrown from the mower. This helps with mulching.

Mower Blades should be sharpened once a year if you mow once a week during a normal three season schedule. With more use you may want to sharpen it more often.

brief how to

In this article, you will find information about:

  1. Disconnect The Spark Plug
  2. Block The Blade From Moving
  3. Use Wrench To Remove The Blade Bolts
  4. Sharpen The Blade Or Purchase A New Blade
  5. Balance The Blade
  6. Attach The Blade
  7. Connect The Spark Plug

tools and materials

    • lawn mower
    • Socket wrench for blade bolts
    • Grinder wheel or file
    • Nail to balance the blade on

step 1 Disconnect The Spark Plug

Remove the spark plug by disconnecting the spark plug wire from the top of the spark plug.


step 2 Block The Blade From Moving

Use a piece of wood to prevent the blade from moving when it is turned. It works well to put the wood thru the discharge chute as shown in the image.


step 3 Use Wrench To Remove The Blade Bolts

Use a wrench to remove the bolts holding the blade on. Bolts are typically attached with two bolts.


step 4 Sharpen The Blade Or Purchase A New Blade

There are two options to get a sharp blade, replace the blade or sharpen the blade. If the blade is badly damaged, dented or bent beyond repair, then you will need to replace it with a new one.

sharpening: If you are able to sharpen it you can either take it to a blade sharpening service or sharpen it yourself using a grinder or file. If the blade has a lot of large dings then you should use a grinder to grind them out. If the blade only needs minor fine tuning then you may be able to use a flat file. Try to grind/file the blade to the same angle as installed when it was made.

blade heat: If using a grinder make sure to not allow the blade to heat up by moving the grinding wheel across the blade and not holding in a single spot long enough to let the blade heat up. Excessive blade heat will cause the blade to lose its temper and therefore not be as strong.


step 5 Balance The Blade

Balancing the blade is critical to keeping your mower running smoothly and to keep it from damaging the mower. A blade out of balance will vibrate and cause pre-mature failure of the bearings that the blade spins on. After the blade is sharpened it may be out of balance because steel has been removed from it.

Use either a blade balancing kit purchased from a store that sells lawn mowers or a nail nailed to a wall. This article shows how to balance a lawn mower blade using a nail.

These are the steps to balance the lawn mower blade:

  1. Put a nail into a wall and hang the blade on it thru its center hole..
  2. Make sure that the blade is centered.
  3. Let go of the blade and see if either side drops.
  4. If one side drops remove steel from the end, not the cutting edge, of the blade that is heavier.
  5. Put the blade back on the nail and check to see if it is balanced.
  6. Repeat this process until the lawn mower blade is balanced.


step 6 Attach The Blade

Make sure there is no grass or other debris to keep the blade from sitting tight against its mount. Attach the blade to the lawn mower. You will need to re-position the wood block so the blade will bind against it when it is rotated in the opposite direction while turning the bolts clockwise.

step 7 Connect The Spark Plug

Connect the spark plug wire to the spark plug. Be careful to make sure the metal tabs that clamp the top of the spark plug are not bent and that they will fit snugly on the top of the spark plug. When you push it onto the top of the spark plug make sure it snaps onto the end of the spark plug.

Lawn Mower Tune Up

After you sharpen the blade you may also want to tune up your lawn mower. This article teaches you how to tune up and maintain your lawn mower to keep it running smoothly.

Todays lawn mowers are built very well which means a long service life. It is important to take care of your lawn mower investment. Proper maintenance will help it last longer, keep it cutting better and help with fuel economy.

Most home stores or small engine repair shops stock the parts for lawn mowers including air filters, spark plugs blades, oil and blade sharpening tools.

step 1 Sharpen The Blade

To sharpen the blade you wil want to remove it from the mower. REMOVE THE SPARK PLUG WIRE FROM THE SPARK PLUG FOR SAFETY. There is a bolt at the center of the blade that you need to remove and then the blade will come off. Make sure there is no fuel in the mower and turn it on its side so that you have access to the blade. Use a block of wood to bind the blade when it tries to rotate in the clockwise direction. Make sure the bolt is clean so that the wrench can get a good hold on the bolt head without stripping it. Put the proper size wrench on the bolt and rotate it clockwise. Remove the bolt and blade.


You can take the blade to a knife sharpening shop or small engine repair shop and have them sharpen it for you. If you decide to do it yourself you can sharpen the blade using a flat metal file or wheel grinder. Remove the metal at the same angle that is currently on it.

Balance the blade. Read the article How To Sharpen A Lawn Mower Blade to learn how to sharpen and balance a lawn mower blade.

step 2 Clean The Air Filter

Remove the air filter and clean it off. If it is not too dirty you can hit it flat against the sidewalk, dirty side down, so dirt and dust will fall out. If you have a air compressor you can blow it off. If it is really bad you should replace it.

step 3 Replace The Spark Plug

Replacing the spark plug is done by removing the spark plug wire and then using a spark plug socket wrench which is usually a 3/4" or 13/16" socket. The spark plug will be gapped at the factory, if you drop it and bend the electrode you will need to regap it. Install the new spark plug, tighten it with the socket until it is snug then turn it another quarter turn, Do Not Over Tighten It! Replace the spark plug wire before starting the mower.


step 4 Replace The Oil

Replacing the oil is done by removing the oil drain plug which is located under the mower close to the shaft that holds the mower blade. Getting the oil out of a mower is sloppy so you will want to work on a surface that will be ok with an oil drip. It helps to put down a piece of cardboard to work over.

  1. Start the mower for a few minutes to warm up the oil. Turn the mower off, REMOVE THE SPARK PLUG WIRE FROM THE SPARK PLUG FOR SAFETY.
  2. Turn the mower on its side and remove the drain plug until you can hand loosen it.
  3. Drop the mower down with the drain plug aligned over the plug. Put your hand under and remove the plug.
  4. After it is drained tilt the mower back on its side and replace the plug, tighten it good enough so that it will not come out.
  5. Put the mower back down on its wheels, remove the filler cap and fill it with oil. Most mowers will need to be filled until the oil is visible and just barely touching the bottom threads in the filler hole. Other mowers have a dip stick with a depth indicator on it.
  6. Replace the filler cap.


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