Abstract: A precision heavy duty indexer characterized in that the indexing member is hydraulically actuated to a locking position whereat it is locked to the indexer housing in desired precise indexed position without circumferential or radial play and without transmission of torque load to the indexer drive means or without transmission of radial load to the indexing member-housing bearings; and is hydraulically actuated to unlocking position whereat it is released from said housing for indexing movement and whereat it is engaged by said drive means operative to index the indexing member to the next indexed position. The indexer herein is further characterized in that the indexer drive means comprises a hydraulic motor driven worm which meshes with a worm wheel having driving engagement with said indexing member, said worm having a sensor-counter thereon to de-energize said hydraulic motor when the indexing member has been indexed through a predetermined angle from one indexed position to the next.