Are Lawn Mower Blades Reverse Thread? [Lawn Mower Help]

are lawn mower blades reverse thread

As is the case with most gardening tools, a lawn mower, whether electric, gas powered or cordless, will require some maintenance from time to time. And, nearly all lawn mowers will require their blades to be removed for either sharpening or replacing.

A question we commonly get asked is “are lawn mower blades reverse thread?”. Technically speaking, it’s not the mower blade that’s reverse threaded but rather the nut that holds the blade in place.

And, there’s a good reason for that. The reverse thread allows the nut to continually tighten as the blade is rotating. This means that it won’t loosen and fall off with every rotation of the blade. However, you may find that not all lawnmower blades use a bolt that has a reverse thread.

Let’s delve into this a little further so that you understand exactly how this works.

Explaining How Lawn Mower Blade Reverse Thread Nuts Work

Most lawn mower blades turn in a clockwise direction. So, if the nut holding the blade in place is tightened in a clockwise direction then it won’t loosen as the blade turns. Conversely, if you have a lawn mower whose blades turn in a counterclockwise direction, then the nut would also be tightened in a counterclockwise direction.

Therefore, each rotation of the blade actually tightens the nut rather than works it loose.

If you want to remove the blade to either sharpen or replace it, remember the following:

  • If your mower blade rotates in a clockwise direction, then you have to loosen the nut in a counterclockwise direction.
  • If your mower blade rotates in a counterclockwise direction, then you want to loosen the nut in a clockwise direction.

How do you tell which way your mower blade turns? For this, you have to check the position of the discharge chute. If this chute is on the right hand side and is angled back, then your mower blade rotates in a clockwise direction.

How To Safely Remove Your Lawn Mower Blades

Your mower blades will wear down over time and you may have to replace them or just sharpen them if you are able to do this. Here are some steps on how to remove the blade safely, especially on a gas powered mower.

Step 1: Make Sure your Mower is Empty

Because you’ll be flipping the mower on its side, you want to ensure that there is no gas left in it. This is not necessary for an electric or cordless mower, of course.

When removing mower blades, make sure that you wear heavy duty gloves to protect your hands. Mower blades and deck edges can be relatively sharp and you don’t want to accidentally cut yourself.

Next, turn the mower on its side. For gas powered mowers, you want to ensure that the air filter is on top. If you flip the mower the other way, oil could leak into the filter and you’ll have a lot of maintenance to do.

Step 2: Disconnect the Mower’s Power Source

For gas powered mowers, you should disconnect the wire from the spark plug and push it out of the way so that it can’t accidentally touch the plug while you’re working on the mower.

For cordless mowers, just remove the battery pack. Electric mowers just need to be unplugged.

Step 3: Put on a Retainer to Stop the Blade from Moving

Once you’ve flipped the mower, you need some sort of retainer to stop the blade from turning while you’re loosening the nut. You could use something as simple as a block of wood wedged between the blade and the side of the deck.

Step 4: Loosen the Nut Using a Wrench and Socket

Most nuts holding the mower blade in position will loosen in a counterclockwise direction. So, it’s just a case of loosening the nut and removing it. If the bolt is really tight, you might need to use a ratchet extension or a breaker bar to loosen it.

As you take the blade off, it’s important to note which way it fits onto the mower so that you can replace it correctly. You need to note which side of the blade is facing outward and which side is facing toward the mower deck.

Also take note in which order the tensioning washers or installed on the bolt.

Step 5: Attach the New Blade

Once the old blade has been removed, you can safely attach the new blade. Ensure that it’s the right way up. Then, tighten the nut in a clockwise direction to secure the blade. Check the user manual for your mower to see what the torque value should be for your particular unit.

Don’t forget to reconnect the ignition wire to the spark plug once you’ve finished replacing the blade.

Frequently Asked Questions

Does a lawn mower blade turn counterclockwise or clockwise?

The majority of lawn mower blades will turn clockwise.

How tight should you tighten a lawn mower blade?

The mower blade should be tight enough so it can’t move on its own. However, you should be able to move it with your hand if you apply some pressure.

Should a lawn mower blade spin freely?

Generally, a lawn mower blade should not spin freely because it’s connected to the engine via a belt.

Why is my mower cutting lower on one side?

This is usually caused by an uneven deck where one side of the deck is lower than the other. You just need to make some adjustments to level the deck again.

Final Thoughts

Most lawn mower blades are connected with a reverse thread nut. This is to ensure that the nut and bolt holding the blade in place doesn’t loosen as the blade rotates.

Remember that to loosen the nut, you have to turn it in the opposite direction of the normal rotation of your mower blades.

Before you change your mower blade, ensure that you’ve disconnected the engine and that you’re wearing gloves to avoid any possible injuries.

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