About serrated chip formation mechanism has many famous assertion. 1964 recht proposed mutations cutting shear instability of the classical model, when the nominal stress-true strain curve slope is zero, i.e., negative impact on the local rate of temperature change is equal to or greater than the strength of the intensity produced by the strain hardening When the positive impact of the material inside the plastic deformation zone will produce mutations cut. Houzhen-bin Oklahoma State University and rangakoⅱ1and raised serrated chip formation process of thermodynamic models, their experiments showed that cutting speed and feed rate plays an important role in the occurrence of instability in shear. samiatin and rab found that when normal flow softening rate of strain rate sensitivity value equal to or greater than 5, the non-uniform flow of the metal cutting process occurs immediately. Instability (strain hardening and thermal softening) thermoplastic process leads generated shear zone, even without thermal softening effect, other mechanisms can also significantly reduce the shear strength of the shear zone. For example, when the shear zone microcracks, so that the actual area under stress decreases, walker and shaw think this is machined in chip fracture of a possible mechanism. Recent studies shaw and vyas cut to lower the processing speed and low-speed machining titanium steel aisi4340 produce nodular chips more clearly confirmed the concept.