Which direction is left-hand thread

Left-hand thread

Most threads are right-hand threads, so you have to turn clockwise to tighten the screw or component. Some components - especially those that are in connection with rotating parts - tend to loosen when using a right-hand thread. Therefore, these components come with a Left-hand thread Mistake.

Components or screws with a left-hand thread are tightened counterclockwise.

Left-hand thread can be found at

Left-hand pedals and right-hand bottom bracket cups are left-hand threaded because of a phenomenon called precession. The phenomenon is not to be understood intuitively, since the direction of rotation that is generated by the precession is exactly opposite to the (substantially) smaller force that is exerted by bearing friction.

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This article is based on the glossary from Sheldon Brown's website. The original author of the article is Sheldon Brown.