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How to sharpen lawn mower blades without removing them?

Lawnmowers are one of the most used garden tools, but they need to be sharp to give a stunning look to your lawn. On average, lawnmower blades should be sharpened twice a year, depending upon the usage. For some owners, that may seem unnecessary as even with dull blades, they’ll 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’ ends. Those can cause the grass to turn brown quicker, and it can also leave your lawn more susceptible to pests and disease. This is not something that lawn owners want. Sharp blades also allow you to cut the grass evenly and quickly, thereby giving you a perfectly trimmed lawn. So, always sharpen your lawnmower blade before the start of the yearly mowing season to get the lawn of your dreams.

How to sharpen lawn mower blades without removing them:

  • Collect the required tools
  • Seal the gas tank. Or, in the case of an electric mower, remove the power cord
  • Tilt the mower and place the wooden block under it on the other side to give it support. The mower blade should be facing towards you
  • Clean the blade with water and a steel brush
  • Use the angle grinder or flat-file to sharpen the cutting edge slowly
  • Lower the mower
  • Unseal the fuel tank

Now that you know the basics of sharpening the blade, it is also important that you go through the details of the process to understand it fully and avoid injury to yourself and damage to the mower.

How to Sharpen the Blades of the Lawnmower?

Given below is the step-by-step guide to sharpening lawn mower blades without removing them. Follow these steps in the given order to sharpen your mower blades while they are still mounted easily.

● Step 1: Preparation

Before starting the sharpening process, get the required tools and follow all the safety precautions:

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

Park your lawnmower on an open flat surface or any workable space. The first thing to do is to remove the spark plug. This will allow you to avoid accidental starting. 

Also, make sure that the parking brake is applied. You don’t want your mower to start rolling while you are working on it.

● Step 2: Seal the Tank and Cut the Power

Remove the gas tank’s lid and place a plastic bag over the gas can’s top, sealing it. After doing this, replace the lid in its previous position. This will make sure that no gas spillage occurs while the mower is tilted.

If you are working on an electric mower, make sure it’s not plugged in.

● Step 3: Tilt the Lawnmower

Tilt the mower into its sideways to access the blade. Whenever you tilt the mower, make sure that the fuel tank and the carburetor are at the top.

Place a wooden block diagonally at the lawnmower’s far side to make it more stable in the lifted position. Make sure the mower is as stable as possible before starting to work. 

● Step 4: Restrain Blade Movement

Now that the mower is secured use another block to restrain the movement of the blade. It would be best to make sure that the blade can’t move in any direction while grinding or sharpening it. 

● Step 5: Clean the Blade

First, use a steel wire brush to remove dirt and/or rust from the blade. While you are on it, clean underneath the mower deck, too, if you find any grass or dirt beneath it. 

Use a bucket of water, putty knife, and brush to remove all dirt and debris from the blades and under the deck.

● Step 6: Sharpen the Lawnmower Blade

After completing the tasks mentioned above, you can proceed to the main job, sharpening the blades. For this job, you can use either a handheld or electric grinder or a metal file, based on their availability and your comfort, and place it over the blade’s cutting edge. Remember always to maintain a proper angle while grinding. After properly sharpening one side, repeat the same process on the other side to finish the job. Since you won’t be taking the blade off the mower, you’ll have to take your time to ensure that both sides are evenly sharpened.

While sharpening, make sure you move the grinder in only one direction and only sharpen the blade’s top face. This means that instead of sharpening with a back and forth sawing motion, you’ll be lifting the grinder every time. Instead of going for speed or rigorous motion, it is best if you grind smoothly and use the grinder’s or file’s entire length in every stroke.

Ideally, try to get an angle of 45 degrees on the top edge while moving the grinder.

● Step 7: Unseal the Fuel Tank

Once you have completed the sharpening process, lower the mower slowly. Plug the mover and, in case of a gas mower, reopen the mower fuel tank lid, remove the plastic bag, and put the lid back again.

This was the last step. Now, you are good to go with clean and sharp blades.

When to Sharpen Your Lawnmower Blades?

There are a few important factors that determine how often you need to sharpen your mower blades. It would be best if you always kept them in mind for the health of the blade.

Most importantly and obviously, it depends on how often and how much you use your mower. In general, after using your mower for about twenty hours, your mower blade will need to be sharpened.  So, if you have an extensive lawn that roughly takes about an hour to cut, your mower will need the blades sharpened after every twenty uses. 

A smaller yard that only takes a half-hour to cut will require all this work after about forty uses.  In general, the more frequently you mow your grass, the more often you’ll need to sharpen the blades.

The age and the overall condition of your mower will also affect how often your blades need to be sharpened.  Cleaning your lawn from garden debris, rocks, and other hard objects can increase your mower blades’ life and efficiency. Checking and cleaning your mower blades before cutting isn’t only so that you don’t spread dirt everywhere but make sure your mower blades don’t get needlessly dull from hitting rocks or tearing other harder objects. It is recommended that you sharpen your lawnmower blades at the start of every mowing season, and then you’ll most likely need to do it one more time during the summer, at least.

The best practice is to check the blades before and after every use to stay updated on the blade condition.

Should Both Sides of a Lawnmower Blade be sharpened?

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

How Sharp Should the Blades be?

The blades don’t need to be too aggressively sharp, but they should have a notable, shiny metal side that has been ground. Sharp blades can be differentiated from dull blades just by their looks and color.

 Keep this simple rule in mind: By the time you have finished sharpening the blade, you shouldn’t grab hold of the edge for fear of cutting yourself.

Important Tips

You need to keep in mind some key tips if you plan to sharpen your lawnmower blades without taking them out. These tips include;

  • Sharpen the mower’s blades on an empty gas tank: Make sure that the gas tank is empty before you start sharpening the blades to prevent any gas spill, leak, or injury.
  • Stay updated on the blade situation: Regularly examine the blades. To know whether the blades are dull, examine the grass blades on your line and check for roughness like any torn or split tips.
  • When to replace the blades: If the mower’s blades are unbalanced, bent, and notched all over, then you need to replace the blades with new ones. This is because such blades are destroyed beyond repair and are not as effective at mowing anymore.
  • Notched blades issue: Notched blades do not necessarily mean your lawnmower blades are useless. This is far from it because such blades can be sharpened and used again.
  • Blades should be correctly balanced: The blades must be well-balanced; or, there will be weird noises coming from the lawnmower. Remember, bluntness is one of the reasons why the blade can be improperly balanced.

Final Remarks

So, is it possible to sharpen the mower blades without separating them from the mower? Well, the answer is yes, and now you can do it as well. By following the guidelines mentioned in this article, you can easily avoid the hassle of removing the mower’s blades for sharpening purposes and do it more easily and efficiently.