GB252618A - Screw thread cutting tool - Google Patents

Abstract

252,618. Baumann, E., and Strasmann, A. Nov. 5,1925. Screwing-dies; ta;ps.-In screw-cutting tools of the kind having longitudinal series of teeth provided with lateral and transverse cutting-edges, the edges of the teeth in relatively adjacent series being oppositely located, the lateral edges conform in shape to the flanks of the thread to be cut and the transverse edges form an acute angle with the axis of the tool. As applied to taps, the teeth which perform the preliminary cutting of the thread are formed with oblique transverse cutting-edges 1a, Fig. 1, the direction of obliquity being opposite in succeeding teeth. The opposite lateral edges may be removed alternately in succeeding teeth as at 3. so that each tooth removes a rough cutting a, Fig. 5, and also a fine cutting b. Alternatively, one cutting-edge may coincide with the flank of the thread itself as in Fig. 15. In the case of taps the lowest points 33 of the cutting-edges lie within the core diameter of the thread and in cutters for external threads they lie outside the largest diameter of the thread so as to true the work to the correct size for the shaping-cutters. For cutting square or trapezoidal threads the taps are constructed as shown in Figs. 7 and 11 respectively, the lateral edges 37, 38 being left full and removed slightly in alternate series of teeth so as to produce rough and fine cutting as shown in Figs. 10 and 14. The cuttings 28, 28<1>, Fig. 10, are produced by each of the teeth 34, Fig. 7, while the cuttings 27, 27<1> are produced by each of the teeth in the succeeding series. Similarly, the teeth 40, Fig. 11, produce cuttings 30, 30<1>, Fig. 14, while the teeth in the succeeding series produce cuttings 29, 29'. In a modification the lateral cutting-edges are not removed in alternate teeth.