Self-drilling screws

Abstract

Abstract 1316157 Self-drilling screws SCHRAUBENKOMBINAT VEB 4 Aug 1970 37628/70 Headings B3C and B3N A self-drilling screw comprises a threadless shaft portion 5 which is initially cylindrical and then tapers outwardly to the maximum diameter of a drill point 6 which has an obtuse point angle when viewed in Fig. 1, the drill point has opposite flat portions 17 which extend to the end of the drill point and form cutting edges 10, 13, spiral grooves 14 extend from the cutting edges into the threadless shaft portions, each flat portion comprises a first part 9 at an angle B2 to a normal to the axis of the screw and a second part 12 at an angle B 1 . The distance a 2 between the cutting edges and an axis of symmetry is greater than the distance a 1 between the point of intersection of the spiral grooves and the flat portions 17 and an axis of symmetry. The angle of a flat portion 17 to the axis of symmetry is α which is designed as an obtuse angle.

Inventors

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