GB477568A - Improvements in and relating to rack cutters for cutting internal gears - Google Patents

Abstract

477,568. Gear-cutting. JACKSON & CO., Ltd., P. R., and MONK, I. Oct. 16, 1936, No. 28117. [Classes 83 (ii) and 83 (iii)] In a method of producing a rack cutter for generating straight or helical internal gears, the profile of a number of the internal teeth a is cut out full size on a templet A which is rotated repeatedly through a small angle about the pitch circle centre, while at the same time a cutter templet D is moved in unison tangentially of the gear, the shape of the gear teeth being scribed after each movement of the two templets and the profile of the cutter being developed from the lines so scribed. The templet D slides between fixed supports B, C, and the lower edge is inscribed for a length equal to the pitch projected from a tooth a with, say, five divisions 1 ... 5 coacting with a fixed mark Z. The templet A is similarly provided with markings 1<1>... 5<1> extending over one pitch, projected radially from the pitch circle centre and coacting with a fixed mark Z<1>. In operation, the marks 1 and 1<1> are first aligned with the corresponding marks Z and Z<1> and the profile of the teeth scribed as shown at 1, Fig. 9, on the templet D. The templets A and D are then adjusted until the marks 2 and 2<1> are aligned with setting marks Z, Z<1> and a similar scribing 2 is made. This process is repeated for each of the markings, giving the other scribings shown in Fig. 9. The inner lines are then developed to obtain the required cutting profile as shown cross hatched in Fig. 9, and the rack cutter finished by the usual methods to this profile. The cutter E is then mounted in a relieving tool box on a slide H, Fig. 10, to generate the internal gear G in the usual way. For cutting double helical internal gears, two rack cutters are used and have their teeth inclined to give the desired helical angle.