Recently, workpiece such as jet engine turbine case has been lightened and thinned for low fuel consumption. However, cutting workpiece of low stiffness that thinning causes contributes to vibration called "chatter vibration". In this study, the phenomenon of chatter vibration occurring on the workpiece is elucidated. By chatter vibration measurement, chatter vibration frequency and chatter vibration mode in cutting were found out. The measurement results turned out that chatter vibration in cutting comes from workpiece's natural vibration. It also turned out that chatter vibration is self-excited vibration, which is caused by coupling two natural vibrations near the cutting tool position.
