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How to sharpen your lawnmower blades

At the end of your grass-cutting season you should make sure to look at the quality and condition of the blades as part of your maintenance, before you store the machine away for winter. It isn’t a particularly complicated process, and spending a little bit of time sharpening your blades can be a serious help for the next time you need the lawn mower.

Depending on how long you’ve had your mower, you may need to replace the blades to ensure an efficient cut. By keeping the mower blades sharpened yearly will help delay replacements, which will ultimately save you money in the long run.

How to know if your blades need sharpening

You should ideally look to sharpen your blades at the end of each mowing season. There are a few telltale signs if the blades aren’t quite at their best, which will often be noticeable in the condition of the lawn after mowing.

If the blades have become blunt, the grass will tear rather than have a smooth cut, which can damage the overall health of the grass. If, a day or so after the grass has been cut, the tips have turned slightly brown. This can also be a clear sign that you will need to sharpen the blades.

Shipshape and sharp

Now you are ready to get cracking there is a simple process that can make sharpening your lawnmower blades quite simple:

  1. Remove spark plug or power cable
  2. Ensure that the spark plug or power cable is disconnected; you want to be 100% sure that the lawn mower doesn’t start accidentally while you are working. Petrol mower blades can spin up to 3000rpm and, trust us, you do not want to be in the firing line should this accidentally start. For petrol mowers you should consult the manufacturers’ manual for instructions on how to remove the spark plug correctly and safely.

    As checking the spark plug will be a part of your overall maintenance of your mower, before you store it away for winter, this should happen anyway.

  3. Remove blade
  4. Now that it’s safe to work, you can remove the blades. Use a wrench to remove the screw that secures the blade to the mower; keep a hold of this screw, as you will need it later when you reinstall the blade, and you don’t want to lose it. The blade may still be fairly sharp so it is advisable to use gloves to protect your hands whilst you remove the blade.

  5. Sharpen blade
  6. To actually sharpen the blade you should use a file or an angle grinder, keeping the blade at roughly 45 degrees. You should check the angle of the existing edge taking time to even out any rough spots. You may find it easier to clamp the blade in a vice to make sure it doesn’t move while you are working.

  7. Check balance
  8. Once you are happy with the sharpness you will need to check the balance of the blade. This is very important as it can, not only affect the cutting ability but also can affect the long-term health of the mower. To check the balance, hang the blade on a nail through the bolt hole in the middle of the mower. If it remains horizontal then it will be ready to reinstall. If it is unbalanced and one side hangs lower than the other, you may need to file a bit more off the edge.

  9. Reinstall the blade
  10. Once you’re sure the blade is balanced and sharpened properly you can reinstall the blade. While the blade is off the mower this provides an excellent time to clean the mowing deck from any debris. This will also help with the efficiency of the mower when you come to use it next.