This document discusses Merchant's circle analysis for orthogonal metal cutting. It introduces key terms like shear velocity, chip velocity, shear strain, and shear strength. It lists assumptions of the model including a perfectly sharp tool, planar shear surface, straight cutting edge generating a flat surface, and uniform velocities. Merchant's circle analysis relates the cutting forces - feed force F, thrust force Ft, and shear force Fs - to the shear plane angle ø and tool rake angle α through trigonometric relationships. The goal of Merchant's circle is to analyze minimum power consumption during metal cutting.