Abstract: A drive motor for driving a tool such as a grinding tool through a right angle drive has a rotatable head mounted on the housing and having a detent on the rotatable head for engaging a fixed component of the angled drive coupling so as to hold the axis of the angled drive coupling at a required angle around the axis of the housing and for adjusting the angle without removal of the right angle drive from the motor. The rotatable head includes an annular disk which surrounds the axis of the motor and has a central hole through which the driven member extends into the chuck. The disk is driven by an adjustment motor having a sprocket which engages gear teeth on the exterior of the disk and has a series of holes through the disk member at angularly spaced locations around the axis so that a locking pin driven by a locking pin motor engages into a selected one of the holes to lock the head at the required angle when rotated to the required angle by the adjustment motor.