Studies on the Internal Gear Hobs : Hobs working like the broach and their cutting test

Abstract

Before this paper, it is pointed out that the barrel shaped hob for generating the internal gears is difficult to make with theoretical exactness, and the conception of using a cylindrical forming hob instead of the generating one is reported. This forming hob has a tooth helix wound once and is made very easily. From the cutting test with the above hob made on trial, a new excellent hob is developed. Present paper describes the designing and manufacturing method of the new hob, the results of cutting test and the instructions for its practical use. This hob has the broach-like teeth wound twice along the helix, and can be made by almost the same technique as the one used in the manufacture of the ordinary hob. An accurate internal gear can be continuously cut with this hob, which will be especially suitable for large internal gear production.