How to sharpen lawn mower blades without removing

How to sharpen lawn mower blades without removing

Lawnmowers are one of the most commonly used garden tools, but they need to be sharp to ensure your lawn looks beautiful. It is recommended that lawnmower blades be sharpened twice a year, depending on their usage. 

Some owners think that's unnecessary, as dull blades will still cut your grass. But the point is that with worn blades, the cut will be rough, leaving behind torn tips on the individual grass blades. This can cause the grass to turn brown faster, and it can also leave your lawn more susceptible to pests and diseases.


This is not what lawn owners want. Blades that are sharp allow you to cut the grass evenly and quickly, resulting in a perfectly trimmed lawn. Therefore, always sharpen your lawnmower blade before the start of the mowing season to achieve the lawn of your dreams.

The following instructions will show you how to sharpen lawn mower blades without removing them:

  • Collect the necessary tools
  • Seal the gas tank. Or, if you have an electric mower, disconnect the power cord
  • Then tilt the mower and put the wooden block under it on the other side to give it support. Position the blade of the mower towards you.
  • Rinse the blade with water and clean it with a steel brush.
  • Carefully sharpen the cutting edge with a flat file or an angle grinder.
  • Lower the mower
  • Unseal the fuel tank
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Step 1: Preparation

Prepare the necessary tools and follow all safety precautions before beginning the sharpening process:

  • Tools: a bucket of water, a wooden block, a steel wire brush, an angle grinder, and a flat file
  • Safety equipment: Goggles, Cut proof gloves

It is best to park your lawnmower on a flat surface or anywhere you can work. Before you begin, make sure the spark plug is removed. This way, you can avoid accidentally starting the engine. 

Also, make sure that the parking brake is engaged. You do not want your mower to roll while you are working on it.

Step 2: Seal the Tank and Cut the Power

The lid of the gas tank should be removed, and the top of the gas can should be sealed with a plastic bag. Once that is completed, the lid should be placed in its original position. By doing so, no gas will spill out while the mower is tilted. When working on an electric mower, ensure that it is not plugged in.

Step 3: Tilt the Lawn mower

To access the blade, tilt the mower sideways. Whenever you tilt the mower, make sure that the carburetor and fuel tank are at the top. Place a wooden block diagonally at the lawnmower's far side to make it more stable when raised. Before working with the lawnmower, make sure it is stable as possible. 

Step 4: Restrain the blade's movement

Now that the mower is secured, it can no longer move, so add a second block to restrain it. It would be best if the blade could not move while it was being ground or sharpened. 

Step 5: Clean the Blade

To begin with, clean the blade with a steel wire brush. Whenever you find grass or dirt under the mower deck, make sure to clean it as well. Use a bucket of water, a putty knife, and brush to remove dirt and debris from underneath the deck and from the blades.

Step 6: Sharpen the Lawnmower Blade

After completing the tasks outlined above, you can begin sharpening the blades. For this task, you can either use a handheld or electric grinder or a metal file, depending on which is more convenient for you and which is most comfortable.

Remember to always grind at the proper angle. After properly sharpening one side, repeat the same process on the other side to finish. Since you won't be removing the blade from the mower, you'll have to make sure both sides are evenly sharpened.

Sharpening the blade requires moving the grinder only in one direction, and only sharpening the top face. In other words, instead of sawing back and forth, you'll be lifting the grinder every time. Instead of grinding quickly or vigorously, it is best to grind smoothly and use the entire length of the grinder or file. As much as possible, ensure that the top edge of the grinder is at an angle of 45 degrees.

Step 7: Unseal the fuel tank.

If you have completed the sharpening process, slowly lower the mower. Plug the mower and, if the mower is gas, open the fuel tank lid, remove the plastic bag, then put the lid back on.

That's it. Your mower blades are now clean and sharp.

When to Sharpen Your Lawnmower Blades?

Sharpening your mower blades depends on a few important factors. It is important to keep these things in mind for the health of the blade. Of course, the most important factor is how often and how much you use your mower. In general, your mower blade needs to be sharpened after about twenty hours of use. 

Therefore, if you have an extensive lawn that takes about an hour to mow, your mower's blades will need to be sharpened after every twenty cuts. A smaller yard that takes a half hour to cut will take all this work after about 40 uses. Generally, the more often you mow your grass, the more often you need to sharpen the blades.

You will also need to sharpen your mower blades based on the age and condition of the mower. Keeping your lawn free of garden debris, rocks, and other hard objects will increase the life and efficiency of your mower blades. Checking and cleaning your mower blades before cutting isn't just to avoid spreading dirt everywhere.

It's also to keep your blades from becoming dull from hitting rocks or tearing other harder objects. In general, it is recommended that you sharpen your lawnmower blades at the start of each mowing season. You will probably need to do it twice during the summer.

The best practice is to check the blades before and after every use so you know how they are doing.

Is it necessary to sharpen both sides of a lawnmower blade?

The answer is no - just like scissors, one side of the mower blades should be sharp while the other side should be dull. A lawnmower blade should have one side sharpened at an angle of around 45 degrees, and the other side left as is (rough), except for smoothing out any uneven edges. If both sides are sharpened, the blades will become unnecessarily dull much more quickly.

What is the optimal blade sharpness?

Blades don't need to be very sharp, but they should have a shiny metal side that has been ground. It is easy to distinguish sharp blades from dull blades by their appearance and color. By the time you have finished sharpening the blade, it is best not to hold on to the edge for fear of cutting yourself.

Tips To Remember

There are a few key tips you should keep in mind if you plan to sharpen your lawnmower blades without taking them out. These tips include:

  • The mower's blades should be sharpened on an empty gas tank: Make sure the gas tank is empty before sharpening the blades to prevent any gas spills or leaks.
  • Monitor blade condition: Check the blades regularly. Check the grass blades on your line for roughness, such as torn or split tips, to determine whether the blades are dull.
  • Blade replacement: If your mower's blades are unbalanced, bent, and notched all over, you need to replace them with new ones. This is because such blades are destroyed beyond repair and aren't as effective at cutting grass anymore.
  • Notched blades issue: Notched blades do not necessarily indicate that your lawnmower blades are useless. The blades can be sharpened and reused repeatedly, so this is far from the case.
  • Proper blade balance is crucial: If the blades are not balanced properly, the lawnmower will make strange noises. Remember, bluntness is one of the reasons why a blade can be unbalanced.

Final Remarks

Is it possible to sharpen the mower blades without having to separate them from the mower? The answer is yes, and you can do it too. By following the steps in this article, you will avoid the hassle of removing the mower's blades for sharpening purposes while doing it faster and more efficiently. 

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