Advanced aeroengine alloys such as titanium and nickel-based alloys are widely used for casing and compressor blades. Poor
machinability of titanium and nickel-based alloys are due to their inherent characteristics, including high hot hardness and strength, causing sinificant deformation of the cutting tool and workpiece during machining, low thermal diffusivity, rapid work hardening, causing a severe wear at the depth of cut line, and the saw-tooth chip formation. For efficient and precise NC machining of these difficult-to-machine materials, an understanding of the cutting mechanism is essential. This paper provides an overview of the theories of saw-tooth chip formation mechanism and the fracture criteria for the FEM simulation of segmented chips. How to determine the flow stress at high deformation rates and temperatures in the cutting zone is then discussed. The interaction between strain, strain rate and temperature should be sufficiently considered. The temperature and residual stress have a considerable influence on the distortion and machining precision for thin-wall structures as used in the aerospace industry, which are also analyzed in this paper.