Abstract: A grinding machine for crowning of internal or external gears, including an indexing mechanism for supporting the gear so as to successively present each of the gear teeth to a gear crown grinding wheel which is supported so as to be moved through an arcuate path as it is drawn across the gear teeth so as to produce a crowning of each respective gear tooth. The arcuate movement of the grinding wheel is produced by a pivotal fixture having first arm extending toward the work holder on which the grinding wheel is mounted. The pivotal fixture is pivotally mounted on an adapter trunnion secured to the machine wheel head and having an opening concentric with and receiving the machine spindle for pivoting movement of the pivotal fixture about the axis of the machine spindle. A belt drive between the spindle and the grinding wheel provides rotative power to the grinding wheel while accommodating the pivotal movement.