GB586925A - Improvements in or relating to manufacture of screw threads - Google Patents

Abstract

586,925. Rolling screw - threads. LANDIS MACHINE CO. May 9, 1944, No. 8805. Convention date, June 9, 1943. [Classes 83 (iii) and 83 (iv)] Chasers; taps.-A tool for cutting a screwthread in a work piece by relative rotation of the tool and the work comprises a plurality of teeth, each tooth having on one or both sides a rough cutting edge and a finish cutting edge meeting at an obtuse angle to simultaneously rough-cut axially spaced portions of a side face or faces of the screw-thread and finish cut to final form, other axially spaced portions of said side face or faces adjoining the rough cut portions. The invention is shown applied to the cutting of a screw-thread by a set of four chasers of which two, A and B are shown in Figs. 2 and 4. The first cutting tooth 31a of the chaser A has an edge 32a for rough forming the first portion of the side of a thread groove, this portion being subsequently finished by the part 35 of the edge of the cutter 31b of the chaser B, the part 34 of the same edge at the same time rough forming the side of a deeper portion of the thread. Similarly as regards the second teeth 22a and 22b of chasers A and B, the parts 55 of the latter finish the thread portions rough formed by the cutting edges 53 and 54. The rough and finish cutting portions of each side of a tooth meet at an obtuse angle. Non-cutting guide teeth 18a and 19a are provided beyond the final cutting teeth 21a, 21b. The invention is applicable also to taps. The Specification as open to inspection under Sect. 91 comprises also a thread-rolling device having rotatable thread-rolling dies so shaped as to have the general profile of the chasers shown. This subject-matter does not appear in the Specification as accepted.