Abstract: 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).

Abstract: 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).

Abstract: A hair styling iron for selectively effecting hair straightening or curling includes a generally circular cross-section electrically heated barrel. A tongue is movable relative to the barrel for selectively clamping a strand of hair between the tongue and the peripheral surface of the barrel for curling hair wound therearound. The barrel comprises a first and second pipes each having a generally semi-circular cross section with a top rounded outer surface and a flat bottom outer surface. The pipes are movable relative to each other between a closed position where the flat bottom surfaces are kept in closed relation to each other and an open position where the bottom surfaces are spaced away from each other. In the closed position, a strand of hair can be held between the opposing flat bottom surfaces of the first and second pipes in order to substantially straighten or uncurl the hair. Thus, the hair styling iron can alone provides hair curling and straightening capabilities.