Chatter

Because tubes are inherently hollow, they have a low dynamic stiffness and act like tuning forks during machining processes like turning or boring. The ratio of the tube's length to its diameter (L/D ratio) dictates its susceptibility to chatter. If the cutting frequency matches the natural resonant frequency of the tube, regenerative chatter occurs. This creates an unacceptable surface roughness (measured as R_a) and can even cause the tube to crack. Machinists often use specialized vibration-damping boring bars or fill the tube with elastomers to deaden these harmonic vibrations.