Rotational indexing device for a machine tool

摘要

A machine tool rotational indexing device is provided that is capable of avoiding or restraining the reduction in the preload force of any of rolling element rows or restraining the reduction in the support rigidity of the rotary-side coupling even if the preload is decreased. Rolling elements are arranged in a plurality of rolling element rows between a rotary-side coupling and a stationary-side coupling and a prescribed preload force acts when a joint coupling is located in an unclamped position. The rolling element rows are constructed of a first rolling element row arranged in a direction in which the preload force increases as the joint coupling moves to a clamped position and a second rolling element row arranged in a direction in which the preload force decreases. The first rolling element row is positioned farther apart from the meshing engagement portion of the couplings than the second rolling element row.