threading die[′thred·iŋ ‚dī]
a threading tool for cutting an external thread manually or on a metalcutting machine tool, usually in a single pass. In the machining process the die and the workpiece perform two relative motions, rotation around the longitudinal axis of the thread and a longitudinal feed equal to the pitch of the thread; the die cuts a thread with its cutting teeth as it is screwed onto the workpiece. The die requires a preliminary forced feed of only one or two turns during cutting-in; subsequent axial motion is produced by self-feeding.
The external shape of a threading die may be circular, square, hexahedral, or tubular. Dies are classified as solid, split, and separable. There are dies for threading heads and metalworkers’ diestocks that cut threads in several passes. The most common type is the circular threading die which, like a nut, has a central threaded hole; the central hole is surrounded by three to six smooth holes that intersect the central hole to form the teeth of the die and slots for removing the chips. Tubular dies are used on turret lathes and automatic machine tools, where the conditions of chip removal are simplified. The cutting speed during the operation of a die is 2.5-4.0 m/min; low cutting speeds are caused by poor heat removal from the narrow cutting teeth. Dies are generally made of tool steel and high-speed steel.
N. A. SHCHEMELEV