A height control for use in connection with punch marking a metallic plate and wherein the distance between the punch marking tool and the plate surface undesirably varies at random due to warping of the metal sheet or deviations from desired tolerance. A microprocessor counter measures the time interval during which the punch marker is in contact with the metal plate. This time interval is compared with a predetermined time range that is indicative of an "in position" condition for the punch marking tool. Detection of time intervals that do not fall within the predetermined "in position" time range results in a pulsed correction signal that activates an electric motor which in turn varies the height of the punch marking tool via a rack and pinion assembly mounted on the tool assembly.