Study of mechanicals of cryogenic cutting BT20 Titanium Alloy was done on X62W milling machine .On the basis of establishing dual planar cutting model , comparing with the transmutation coefficient of the chip between ordinary and cryogenic cutting , researching of the mechanism of transmutation coefficient of the chip is carried on. Experiential equation of cryogenic cutting BT20 Titanium Alloy is established on basis of experiment and studying the quality of workpieces’surface and reseaching the mechanica...