Left Hand Nut

A left hand nut has a thread that tightens anticlockwise. It is used where rotation could otherwise loosen a standard right hand nut.

A left hand nut tightens anticlockwise onto a matching left hand thread. It resists loosening on shafts or fittings that turn in that direction. It takes a bolt or stud of the same left hand thread and is turned with a spanner.

Nuts of this kind are often made in low carbon steel, which suits general fixing work where high strength is not needed. The grade shown is a common commercial grade for light duty use.

This is a general guide to checking this kind of part. It says nothing about any supplier's parts.

Ask for a certificate of conformance and a mill test certificate. On receipt, check the thread direction and the grade marking.