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An experimental device, based on the light-gas gun technology, was set up to realize high speed cutting over a wide range of cutting speeds from 30 m/s to 200 m/s. High-speed cutting experiments were performed on AISI 1045 steels. The investigation of chip morphology, micro-structures, micro-hardness and the finished surface integrity were carried out, focusing on the physical phenomena accompanying the saw-tooth chip formation. The results reveal that, with increasing the cutting speed, the transition of chip morphology from continue to saw-tooth could be attributed to repeated thermoplastic shearbanding rather than periodic cracking. In particular, a severe material flow leading to mass transfer of heat was observed at very high cutting speed. The effect of mass transfer of heat on thermoplastic shear instability was further investigated, which implies that the mass transfer of heat would retard the formation of saw-tooth chip. Finally, the influence of cutting speed and mass transfer on the temperature distribution during high speed machining was briefly discussed.

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