The energy released during mechanical cutting is carried away by the metal chips and conduction into the tool. This report focuses on determination of the heat fluxes into the tool during orthogonal cutting using Beck's method. An infrared camera is used to measure the temperature rise on the surface of a cutting tool during turning of aluminum A390 cylinders. A detailed model of the tool in FLUENT is used to compute the sensitivity coefficients for the temperature response at specified sensor locations due to a unit heat flux disturbance at the cutting zone. These sensitivity coefficients are used in Beck's method along with the measured temperature history, to determine the heat flux history at the cutting zone.