Abstract: A general safe retract and return function is provided for a machine tool which is easily programmed for all cases to avoid collision and interference between the workpiece and tool and to reduce the damage or imperfection in the surface of the machined workpiece caused by the termination and/or resumption of machining. The general safe retract and return function includes parameters defining incremental retract and entry vectors relative to the direction of the machining path in the region of the interrupted point. Preferably the tool and workpiece are reengaged at the interrupted point along an entry ventor which is at a grazing angle with respect to the reverse of the tool feed direction along the machining path, thereby avoiding remachining of the workpieces but providing a smooth surface finish.