What is the root cause of 'chatter' during a milling operation, and how can it be mitigated?

The root cause of 'chatter' during a milling operation is self-excited vibration. Chatter is a cyclical, unstable vibration between the cutting tool and the workpiece that results in a characteristic squealing or rattling noise and a poor surface finish with visible undulations. This vibration is self-excited because the cutting process itself generates the forces that sustain the vibration. The cutting tool, the workpiece, and the machine structure all have natural frequencies at which they tend to vibrate. If the cutting forces excite these natural frequencie....