SCREW TAP Russian patent published in 2003 - IPC

FIELD: machine engineering, mechanical working of materials, thread cutting. SUBSTANCE: screw tap includes shaping portion and inlet cone with teeth having arranged successively along height portions for plastically deforming with different profile angles. One of said angles is equal to profile angle of screw tap. In order to effectively cut thread of threaded joints, screw tap is double-start one. Shaping portion of first start is in the form of plastically deforming portions; shaping portion of second start is in the form of cutting portions arranged after plastically deforming portions of inlet cone with less profile angle. Plastically deforming portions of each start of inlet cone have different height according to relation H = (1.1 - 1.6)h, where H - height of profile of plastically deforming portions of first start; h - height of profile of plastically deforming portions of second start. EFFECT: improved design providing enhanced accuracy and high reliability of threaded joints. 1 dwg