How Do I Know If My Lawn Mower Blade Is Sharp? (Solved & Explained!)

If you notice mowing is more difficult and takes longer than usual, you may have a dull mower blade. A dull blade cuts grass unevenly and can put more strain on the motor. Therefore, it’s important to sharpen the blade after every 20 – 30 hours of use.

In this article we’ll explain the warning signs to watch out for when your mower blade begins to dull, how to sharpen it, or when it needs replacing instead.

What are the signs my lawn mower blade needs to be sharpened?

If you start to notice the following things when mowing, your blade might be dull and in need of sharpening.

  1. A dull blade cuts inefficiently and unevenly, accumulating nicks and dents due to general wear and tear.
  2. As you cut, you start to notice it takes longer and longer to cut the same area of grass, and the grass length becomes uneven in places, requiring you to redo areas you’ve already cut.
  3. The grass itself may be torn or pulled from the ground rather than sliced cleanly. This can pull chunks of dirt from your lawn, leaving it an unsightly mess.
  4. It might become more difficult to push the mower and may stall more frequently as it struggles to cut without grass getting stuck in the blade. On the bright side, you get a free workout!

Can a dull blade damage my lawn?

Mowing your lawn with a dull blade can result in an uneven cut, tear chunks of dirt out of it, and even cause patches of grass to turn brown and die.

This is because a dull blade rips or tears the grass instead of surgically splitting it, which causes it to become susceptible to disease and start to die, turning a once bright green lawn into a yellow, splotchy mess. If you want a good looking lawn, always make sure that your lawn mower blades are shapened after a few cuts.

Why do I need a sharp lawn mower blade?

Whether you have a ride-on grass cutting machine or a humble walk-behind chugger, a dull blade can seriously hamper not only the appearance of your lawn, but also reduce the efficiency of your mower.

A dull blade causes the motor to work harder, costing you more in fuel and ultimately reducing the lifespan of your mower. Next, we’ll cover how you can remove the blade and what tools you’ll need to bring it back up to speed.

How do I sharpen a dull lawn mower blade?

Simply follow these easy steps to keep your blade razor sharp, and grass quaking in its boots.

  1. Acquire the right tools for the job. You’ll need a wrench, or ratchet and socket for removing the blade, and a file, grindstone, or angle grinder for the sharpening.
  2. Remove the blade. Unfasten the nut and remove the washer that holds the blade to the drive shaft.
  3. Clean the blade. Use a scraper to remove grass, and for more stubborn dirt apply penetrating oil for 30 minutes before wiping with a cloth.
  4. Sharpen the blade. Use your preferred sharpening tool mentioned above, ensuring to wear safety glasses to protect yourself from sparks.
  5. Check that the blade is aligned properly. Sharpening can remove more metal from one side of the blade and result in an uneven cut. Balance the blade on a screwdriver and adjust until it is perfectly balanced.
  6. Replace the blade. Put the sharp blade back into the mower and fasten the nut and washer in place using a torque wrench.

How can I keep my lawn mower blade sharp?

Now that your blade is sharp enough to shave with, you’ll want to maintain that razor edge as long as possible to get the most out of your mower.

Clear your lawn of any large sticks or pebbles before cutting, to avoid damage to the blade. Rust is your enemy, so when you’re finished giving your lawn a much-needed manicure, clean the blade with methylated spirits and a cloth, and store in a dry garage.

How much does it cost to sharpen a lawn mower blade?

If you have the tools and know how, sharpening a blade will only cost you time. If, however, you find that you’re strapped for time, it’s relatively cheap to pay for mower maintenance services.

Mower manufacturers Weingartz provide sharpening services for walk behind mowers from $7.95 on mower to $24.95 if the blade is still attached. They also provide general maintenance packages for everything from oil changes to changing air filters and more.

Does cutting long grass make a lawn mower blade dull faster?

Like many things in life, consistency is key. If you cut your lawn often, you’ll find that your blade stays sharper for longer, giving you a beautiful end result that will make your neighbors envious.

When cutting the lawn gets tedious and you only sporadically maintain it, the long grass that takes over your yard becomes much more difficult to cut. This puts more stress on not only the motor, but also the blade, requiring you to sharpen and replace it much more often.

How many times can I sharpen a lawn mower blade?

Eventually, you’ll find that your blade has reached the end of its life and can simply not cut one more blade of grass. Fortunately, most blades can survive 5 – 6 rounds of sharpening before they give up.

This means in the best-case scenario, most blades can last 150 to 180 hours before you’ll have to replace them.

How do I know when to sharpen or replace my lawn mower blade?

Now that is the question. When your blade completely loses its edge, develops serious cracks, or large dents, it’s time to retire it for good.

Fortunately, blades are inexpensive, easy to replace, and readily available from most hardware stores or directly from the manufacturer. You can pick one up for around $30, so the bank will remain decidedly unbroken.