The objective of this research is to illustrate the importance of modeling the right/similar chip formation with experimental results. When machining ‘difficult to cut’ materials at high cutting speeds, segmented chips are usually formed. When modeling the cutting process, it is important to consider the type of chip formed, as this affects the stress field generated in the workpiece. The modeled chips have to be the same type as those obtained during experimental work. However very few published models were capable of modeling the 3D oblique cutting with segmented chip formation. This paper presents a finite element model that includes a user customized catastrophic slip criterion and crack propagation module to model segmented chip formation in orthogonal & oblique machining of hardened AISI 4340 steel (52±2 HRC). Predicted cutting forces and chip thickness for segmented chips were in close agreement with experimental data. The modeled plastic strain and temperature distribution/magnitude were very different for continuous and segmented chip formation.