Unf thread series, 40 thread quantity per inch, 0.138 inches nominal thread size

An internally threaded item with a cylindrical and/or square, hexagonal, octagonal, or dodecagonal outer periphery (parallel to the threaded axis) a portion(s) of which may or may not be enlarged, forming a flange(s) and/or shoulder(s). Items not having an enlarged outer portion may be threaded, a part of the full length, or tapped from both ends. Items having an enlarged outer portion (flange(s) or shoulder(s)) may be threaded the full length, threaded a part of the full length, or tapped from both ends. Items tapped from both ends shall have either right-hand threads on both ends or left-hand threads on both ends. For items conforming to any of the above and having a length overall exceeding two times the largest outside diameter or width across flats, use post, electrical-mechanical equipment. For items with an outside contour that is the same the full length, having a continuous thread through its entire length, and the length does not exceed two times the diameter or width across the flats use nut (1), plain (as modified). Excludes:nut (1), plain, cap. See also turnbuckle body.