The present contribution is an attempt of the optimal machine tool control in turning to follow a desired tool position with better surface finish characteristics. In order to evaluate surface finishes during machining, a new simple measuring system has been proposed which uses an optical parallel substrate based on a light reflection technique. A tool position control by the LQI control is designed to reduce the tracking error between the tool and the workpiece surface. For this aim, a compensatory flat tool attached to the specially designed tool servo system is compensated for so that the tracking errors in following a desired tool position are removed. The improvements in surface finish are clarified by the roughness measurement with a stylus instrument.