Method of Manufacturing Screw Thread and Screw Thread

摘要

The removal starting position (8S1) of a first removal process and the four removal starting positions (8S21-8S24) in a second removal process are established on an imaginary circle (7I) with a prescribed radius (R) that is inscribed in the apex (7C) of an incomplete thread part (7a). In each removal process, the tip of the screw thread cutting tool shaves off the apex (7C) of the incomplete thread part (7a) into respective recesses, contacting the imaginary inscribed circle (7I) from the outside (above). The multiple cutting surfaces of the apex (7C) are formed in parallel helices (that is, as mutually adjacent helical recesses) from the starting position to the ending position of the incomplete thread part. Points and burrs in the incomplete thread part can thereby be eliminated or reduced without loss of the ability to screw together with a partner threaded fastener (threaded portion).