Left Hand Nuts

Left hand nuts look like regular nuts but are threaded opposite of "standard" (right-hand) nuts. Consequently, turn them counterclockwise to install and tighten. Often abbreviated "LH" for left-hand, use left hand nuts with left hand threaded bolts, screws, studs and threaded rod. They are also known as:

reverse threaded nuts.

There are two types of left hand nuts commonly available: hex and heavy hex. They cannot be used with right-hand threaded fasteners.

Threads are Unified inch coarse series (UNC, Unified National Coarse) or Unified inch fine (UNF, Unified National Fine) and, being left-hand, are reverse threaded compared to "standard" nuts.

Left hand nut size refers to its nominal thread diameter. Typically, sizes range from 1/4" to about 2". Size is specified in inches, usually fractional rather than decimal. Not all types are available in all sizes.

Steel, plain finish, is a common material and finish. (Plain finish is unplated so there is no surface treatment to inhibit rust.)

The different types of left hand nuts are described in Table 1 below…

**Table 1. Left Hand Nuts.** Common nut types that are available with left hand threads.
Left Hand Nuts
Left Hand Hex Nuts
Hex nuts are general purpose nuts. They are most often found in sizes of 1/4" and larger.
Left Hand Heavy Hex Nuts
Compared to standard hex nuts, heavy hex nuts offer added strength from increased thread engagement, which is due to their additional thickness. Their bearing surface is also larger because they are extra wide.

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