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Are Mower Blades Reverse Threaded?

lawnmower image by sumos from

Lawnmowers help to maintain lawns and cut grass. However, as with all machines, lawnmowers require regular maintenance and care. Removing your blade for sharpening or replacement will require the use of a socket wrench to unbolt the lock nut, which is often reverse-threaded.

Blade nuts

Most lawnmower blade nuts are reverse-threaded in order to secure the blade on the drive shaft of the engine. This ensures that the blade's rotation does not loosen the nut. However, not all blades use a reverse-threaded nut to secure them to the engine's drive shaft.

Blade Removal and Installation

When removing a blade for maintenance, sharpening or replacement, it is important that the blade is level. Most lawnmowers use a metal plate above the blade to make sure that it is level. If the blade is reinstalled upside down, then it will not cut your grass. According to Yardener, the lawnmower blade should be replaced every two to three years, depending upon the size of your yard. A portable rotary tool with a grinding stone attachment can be used to sharpen the blade.


It is recommended to remove the spark plug wire before removing the blade. Some lawnmowers also have blade-lock gadgets that help to lock the blade in place while removing and reinstalling it. The blade lock not only keeps the blade from moving while you are trying to turn the lock nut, but also acts as a safety measure for the engine starting while you are working on it.

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