on a grinding machine , a workpiece having eccentric cylindrical portions is rotated around the work spindle axis so that the eccentric cylindrical portions effects a planetary motion . a grinding wheel is reciprocated toward and away from the work spindle axis in synchronism with the planetary motion and is also fed toward the work spindle axis to grind the eccentric cylindrical portion into a target cylindrical profile . upon completion of a part of the grinding operation , the eccentric cylindrical portion under machining is indexed to a predetermined angular position . a diameter measuring device is moved from its rest position to a measuring position to measure the diameter of the eccentric cylindrical portion . comparing the measured diameter with a target diameter to obtain a residual difference in diameter , the grinding machine further operates to perform a finish grinding according to the residual difference until the diameter reaches the target size , whereby the eccentric cylindrical portion can be finished precisely using a general purpose measuring device .