This document discusses mechanics of metal cutting and orthogonal cutting models. It explains that calculating cutting forces is important for determining power consumption, machine design, and tool condition monitoring. Two dimensional and three dimensional cutting models are described based on whether one or two force components are considered. Key terms related to cutting forces and velocities are defined. The orthogonal cutting model makes assumptions to simplify analysis and describes how cutting forces can be calculated based on rake angle and shear angle. Stresses on the shear plane and tool face are also discussed. Finally, methods for measuring cutting forces and power are outlined.