As the machine tools are shifting to high precision cutting, it is necessary to develop an effective instrumentation system and to establish an evaluation method for the spindle run-out error. In this paper, a new measurement system for the run-out error was developed by utilizing an transmitted light beam method. Also a new evaluation method was established by separating the run-out error into rotational error and tool chucking error. The measuring principle is based upon edge detection

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... ue in which a halved photo detector is used to quantify the amount of the transmitted light through the both sides of the pin-gauge used as a master specimen. By providing two similar optical setups which are placed perpendicular to the rotating axis of the pin-gauge, an X-Y displacement measurement system of the pin-gauge was built up. The run-out error of the spindle can be known directly by evaluating the displacement of the pin-gauge through its Lissajous figure. Finally, it was clarified that the performance of the developed evaluation system is practically acceptable.