Abstract: A system for monitoring a machine tool under automatic control is provided which uses the actual path of the tool in all directions of motion for comparison with a mathematically ideal path to detect tool error. Machine tool position is obtained from independent feedback devices on each axis of tool movement. The system monitors the machine control commands independently of a machine control command generating means, the machine control command generating means commonly bring a computer of a conventional type. Thus, a monitoring loop is placed about the entire machine tool, that loop being capable of detecting malfunction or mispositioning of the tool, as that tool operates under automatic control. An independent dynamic braking means enables the system of this invention to bring the machine to a stop without part scrappage in the event of a machine shut down, occurring for example, because of a power system failue, or mispositioning error detection.