Lawnmowers are a fundamental tool for property owners for whom keeping lawns well maintained and trimmed is important. But like all power tools, regular maintenance is necessary to keep your mower performing and increase its lifespan.

One of the chores involved in lawnmower maintenance is the removal of lawnmower blades for the purpose of cleaning them or sharpening them. These tasks should be performed at least once annually, if not more often.

this is a lawnmower

Lawnmower Blade Removal

If you own a walk-behind lawnmower, the blades are generally held in place thanks to what is known as a threaded hex-headed bolt. This bolt will screw into the blade adapter found fitted on the driveshaft of the lawnmower engine. 

To remove a mower blade for sharpening or replacement, the retaining bolt for the blade needs to be turned out so you can remove the blade from the mower.

Are Lawnmower Blades Reverse Threaded?

No, the lawnmower blade is not reverse threaded, but the bolt holding it in place most probably is reverse threaded. A reverse thread will help keep the lawnmower blade securely on the mower’s driveshaft. This is an important attribute in lawnmower operation because it impedes the blade from loosening the nut as it rotates. 

However, not every lawnmower will have a reverse threaded bolt and nut.

Lawnmower Blades are using cutting the grass

How Does a Lawnmower Blade Function?

Lawnmower blades are the machine component that gives you a reason for using this powerful tool. They are the machine parts that actually cut your grass, and they are one of the principal features one considers when evaluating a lawnmower for purchase.

This one machine part is crucial to a lawn mower’s value and its performance.  Precisely due to the importance of the lawnmower blade, threading becomes fundamental because it enables the blade rotation and movement.

When considering threading on rotating machine parts, the threading itself is created in such a way as to tighten the object or part that rotates as opposed to loosening it. In this way, this part will remain firmly attached to the frame from which it rotates.

How Does It Work?

The reverse threading will turn the lawnmower blade center in the opposite direction of the blade’s cutting direction rotation. The securing nut is designed specifically for this purpose.

What Does Reverse Threaded Mean?

When referring to reverse threading, it simply means that a nut has a right-hand thread that loosens when it is turned to the right or in a clockwise direction. On the contrary, tightening will be done by turning the bolt to the left or in the counterclockwise direction.

Lawnmower is cutting the  grass

Are Lawnmower Blades Reverse Threaded?

As a rule, most blade nuts used on lawnmowers are reversely threaded to ensure that blades remain securely attached to a lawnmower engine’s driveshaft. This simple characteristic guarantees that as your lawnmower’s blade repeats rotations, the reverse threaded bolt will in no way be affected or risk loosening.

Nonetheless, not every single lawnmower will feature a reverse thread bolt in its design offering this guarantee.

When you want or need to remove a lawnmower blade for replacement, cleaning, or sharpening, the first thing to verify is the direction of the drive shaft rotation. This is important so you know if the rotation of the blade will eventually loosen the nut.

Walk-Behind Lawnmower Blade Rotations

If your lawnmower is a walk-behind model, many of these models have blades that rotate in the clockwise direction to the right. When removing blades from these mowers the retaining bolt will need to be turned to the left in a counterclockwise direction for loosening and removal. 

Always make sure your mower is positioned on its side during blade removal. The engine’s air cleaner should face upward, and you need to block the blade, so it does not move or turn while you remove it. This is crucial to avoid injury. Also, place the retaining bolt in a secure location so you can find it easily when completing your maintenance by returning the blade to its operational position.

Which Tool?

As most lawnmowers use reverse threaded nuts when removing the lawnmower blade, you will need a socket wrench to be able to unbolt the nut used in locking because it is reverse threaded.

Wear safety gloves to protect your hands from cuts and follow any safety procedures that the manufacturer indicates in the user’s manual.

Conclusion

Are lawnmowers blades reverse threaded? No, the lawnmower blade itself is not. It is the retaining nut and bolt that will be reversely threaded. Remember that this is a general rule, and there may be lawnmower designs that are exceptions.

The mower’s reverse thread retaining nut and bolt will keep the lawnmower blade securely on the mower’s driveshaft preventing the mower blade from loosening the nut as it rotates when cutting the grass.

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