Abstract: A high-speed forming tap (1) for cutting and forming a female screw by cutting edges (E) of a screw portion (2) fed in synchronous with the rotation of a machine tool. The high-speed forming tap is characterized in that chamfers (CF) are provided at a bevel lead (2a) of the screw part (2). The chamfers (CF) start from the cutting edge (E) and are provided along ridgelines (R) between a crest face (2e) and flanks, or a following flank (2c) and a leading flank (2d). This structure enables the shape of the edges of the tap leading portion to be stably maintained and high-speed, smooth female screw cutting with high accuracy, and provides a tap with long life.

Abstract: A shape of a screw for fastening thin-sheets or thin-walled parts is characterized in that a value of ratio (P/D) of a pitch (P) to each of nominal diameters (D) of coarse thread in the shape of screw thread is reduced as compared to values of ratio of pitches to a corresponding nominal diameter of coarse thread in known kinds of screw thread standard, and the multiple number of thread start is set to 2 or more. Thus, for the thin-sheets and thin-walled parts in which three engaging ridges of screw threads cannot be secured when current metric coarse thread screw is used, the shape of the screw thread advantageous in strength and excellent in loose torque after vibration can be provided, since screw fastening is stabilized more than a case in which the metric coarse thread screws are used.

Abstract: A high-speed forming tap (1) for cutting and forming a female screw by cutting edges (E) of a screw portion (2) fed in synchronous with the rotation of a machine tool. The high-speed forming tap is characterized in that chamfers (CF) are provided at a bevel lead (2a) of the screw part (2). The chamfers (CF) start from the cutting edge (E) and are provided along ridgelines (R) between a crest face (2e) and flanks, or a following flank (2c) and a leading flank (2d). This structure enables the shape of the edges of the tap leading portion to be stably maintained and high-speed, smooth female screw cutting with high accuracy, and provides a tap with long life.