Method of rolling worm gear and the worm gear

Abstract

A worm is formed by rolling to reduce the number of processing steps while ensuring the worm accuracy satisfactorily. A work material is positioned between a first rolling die () and a second rolling die () by rotation of the rolling dies and a servomotor () for feeding the work material. When the lead angle of a worm is large and there is a large difference between the finished diameter and the blank diameter, the lead angle changes during the progress of rolling process, resulting in occurrence of through-feed. A slide plate () is freely slidable on a slide (). Therefore, when through-feed occurs owing to the lead angles of the first and second rolling dies () and () and the workpiece, the slide plate () slides freely, and this is detected with a detecting sensor. The rotation of the first and second rolling dies () and () is stopped. Then, the first and second rolling dies () and () initiate reverse rotation, and at the same time, the slide plate () also initiates movement in the reverse direction. Thus, rolling is started. Thereafter, similar processing is repeated to perform rolling.