How to Safely Sharpen Lawn Mower Blades

Choosing From a Variety of Tool Options

Person filing a mower blade to sharpen it.

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Although you may think of sharpening your lawn mower blade as a matter of mower care, it is actually a matter of lawn care. Dull blades are more likely to tear grass blades instead of cutting them cleanly. Such tears open up your lawn grass to an attack from diseases. Fungal diseases love to take advantage of open wounds in plants, especially in conjunction with moist conditions. Mowing the grass creates such conditions because cutting the grass blades releases some of the moisture content that they carry inside.

Tools for Sharpening Lawn Mower Blades

Now that you know why it is important to sharpen lawn mower blades when they are dull, let's find out the best way to do the job. You have a variety of sharpening tools from which to choose, including both manual tools and power tools. Knowing which is the right one for you depends on how much you mow and on your landscaping budget

If you want to cut lawns for a living, then you will almost surely want to own one of the high-end power tools sold for the purpose. These so-called "grinders" do not come cheap. You can expect to pay $700 or $800 for a good one.

Since homeowners do much less mowing than the pros do, they are better off choosing from among a number of options for manual tools and lower-end power tools. If your priority is saving money, then that old manual standby, the humble file, is certainly an option. For those who already own a Dremel tool (or do not mind investing in one), the Dremel A679-02 Attachment Kit is a great choice, providing a guide that helps you do the job right. Buy on Amazon.com.

But far more homeowners already own a power drill than own a Dremel tool, making drill attachments sold specifically for sharpening lawn mower blades the most sensible choice. VintageBee sharpeners are an example. A VintageBee sharpening attachment consists primarily of a blue plastic guide and a gray sharpening stone. Buy on Amazon.com.

Assuming you choose to sharpen your lawn mower blade with a drill attachment, here are the tools and other supplies that you will need for the job:

  • Power drill
  • Sharpening attachment
  • Blade balancer
  • Workbench
  • Vise
  • Wrench
  • Safety gloves
  • Safety glasses

What You Need to Know Before You Sharpen

Before beginning, and regardless of which tool you choose to use, you need to know:

  • How sharp the blade should be
  • When sharpening is not enough
  • How often to sharpen

Because you are undertaking this project to correct the dullness of your blade, you might think that you should be aiming for the sharpest blade possible. Unfortunately, it is not that easy; a delicate balance is called for. The cutting edge of the blade needs to be sharp, but it should not be razor-sharp. A razor-sharp edge will not hold up for very long at all, meaning you will soon have to sharpen it again.

If you detect large nicks or bends in your blade, no amount of sharpening will correct the problem. Instead, you need to buy a new lawn mower blade. Sharpen your blade every other month.

How to Sharpen Lawn Mower Blades With a Drill Attachment

  1. For safety, take off the spark plug wire so that the lawn mower cannot start up accidentally.
  2. Flip the mower over and remove the lawn mower blade with a wrench. A nut (or nuts) holds the blade up against the underside of the mower deck.
  3. Secure the blade in the vise that you keep on your workbench.
  4. Attach the drill attachment to your power drill.
  5. Insert the cutting edge of one end of your lawn mower blade between the blue plastic guide and the gray sharpening stone of the attachment such that the guide is resting up against the rear of the cutting edge. 
  6. Press the trigger on the drill and run the attachment along this part of the blade.
  7. Remove the blade from the vise and flip it over so that the cutting edge of the other end of the blade is pointing up; sharpen it in the same way.
  8. Be sure to sharpen each side of the blade an equal amount to keep your blade in balance. Check for balance with a blade balancer.