Abstract: A device for automatic advance of a rotating tool towards a workpiece, which includes a rotating tool holder for holding a cutting tool for operation on the workpiece. A gear wheel bears against the rotating tool holder which forces it toward the workpiece. A holder is provided to secure the gear wheel with respect to the workpiece. A device associated with the rotating tool holder engages the gear wheel and rotates it as the tool holder rotates. Associated with the holder and the gear wheel is a mechanism for advancing the gear wheel towards the workpiece as the gear wheel rotates. A stop motion apparatus associated with the gear wheel and the rotating tool holder is included for stopping the rotational movement of the gear wheel. The stop motion apparatus consists of a non-rotatable cam which operates on the cam follower to disengage it from the gear wheel, stopping the rotating movement thereof during a segment of the rotation of the tool holder.