3b thread class, 0.235 inches minimum and 0.265 inches maximum length, 0.250 inches maximum width across flats, 0.250-20 unjc-3a insert size, 0.032 inches minimum and 0.042 inches maximum top portion unthreaded outside length, 36 thread quantity per inch

A cylindrical item which may have wrenching and/or driving facilities and/or shoulders. It is designed to be inserted in a drilled, tapped or a pretapped hole, or molded or pressed into soft material to reduce the size of a tapped hole; to provide threads; to add strength, and/or to prevent stripping. It is one of the following: (1) a one-piece, flanged or unflanged, internally threaded item which may have external threads, and/or serrations around the periphery of the collar, designed to engage a serrated lock ring which is not included with the item; (2) a one-piece precision coiled wire; (3) a two-piece item consisting of an internally threaded cylinder and a mating externally threaded part; or (4) a one-piece internally threaded item whose outside diameter is tapered and/or knurled and/or with fin(s). The internal thread of the item may have a locking feature. Excludes:items having a sleeve on on its under portion which can be clinched or crimped. Excludes:bushing,machine thread; nut,plain,knurled; nut,plain,round; nut,plain,clinch and nut,self-locking,clinch. See also nut,plain,plate