Left-handed taps and dies

Left hand thread

— dies and taps (see "Type") designed for cutting left-hand threads.

The standard modern thread (which tightens clockwise and loosens in the opposite direction) is right-handed in the direction of the helical surface: if you look at such a thread from the side, for example, on a bolt, its turns will go from left up to right. In a left-hand thread, accordingly, everything is the opposite — the turns are directed from right up to left, loosening is done clockwise, and tightening is done counterclockwise. Such threads are used noticeably less often, however, in some cases they are preferable to right-hand threads, and sometimes they are the only suitable option. Accordingly, left-hand dies and taps are also available for sale, although noticeably less frequently than right-hand ones.