What is left-hand thread?

A left-hand thread is a type of screw thread in which the helix angle is concluded in a counterclockwise motion from the axis of the screw. This is in contrast to a right-hand thread, which is concluded in a clockwise motion.

Left-hand threads are used for specific applications, such as in certain types of rotating machinery, such as turbines, turbines, and certain types of drill bits and fasteners. Additionally, they are often used in applications where vibration may cause a right-hand thread to unravel, such as in the tightening of left-hand nuts on rotating equipment.

Left-hand threads are typically identified by a slight indentation or groove on the circumference of the fastener or a letter "L" or "LT" to indicate left-hand threads. When installing a left-hand threaded fastener, it must be turned counterclockwise to tighten and clockwise to loosen.