The high performance of the hourglass worm gearing, especially whose worm teeth are hardened and ground by conical grinder has become widely recognized. But this hourglass worm gearing has next outstanding problems. Namely, (1) The difficulty of the manufacturing of the hob cutter and maintenance of its accuracy. (2) The poor cutting ability of the hourglass worm teeth. Therefore we propose new methods to solve these problems. Namely, (1) Grinding method for worm wheel teeth by electro-deposited diamond wheels. (2) Generation for worm teeth by Mach type cutter. We actually manufactured new hourglass worm gear set by these new methods of manufacturing. And also we tested new hourglass worm gear reducer with these gear set and proved its high performance.
