| 摘要 |
A method of producing a self-tapping screw from a screw blank 10 with a shaft part 11 and an adjoining shaft end in the form of a truncated cone 14, wherein three flat segments 16 are formed on the shaft part 11 parallel to the axial line of the blank, while a length of the shaft end 14 configured as a truncated cone remains right circular. A delta-shaped region 19 is formed at the head end of each flat region 16 with an arc-shaped convex surface peripherally and narrowing toward the flat segment. By thread rolling which leaves behind the outermost part 15 of the shaft end 14, a spoonlike recess 24', 25', 26' is formed at the top segment of each thread 24, 25, 26 at the flat segment to form the machined outer threads. The depth of the spoonlike recess decreases in succession at the delta-shaped region 19 to produce properties which equalise the torque increases. <IMAGE> |
