This paper provides data along with experimental evidence of ductile material separation that supports the Atkins' model of machining, which includes the energy needed for material separation along with shear and frictional dissipation. This model proposed earlier explicitly includes the energy needed for material separation in addition to that needed for shear and friction. However, no experimental evidence for material separation via ductile tearing or fracture was provided. In this work, orthogonal cutting is performed on oxygen-free high conductivity (OFHC) Copper, a highly ductile metal, at very low speeds and low uncut chip thickness where size-e ect is observed. The chip-workpiece interface is observed under a scanning electron microscope to nd evidence of material separation via ductile fracture. For values of fracture toughness and shear yield stress, that are of the same order of magnitude as that reported in the literature for OFHC Copper, the Atkins model captures the trend and the predictions are seen to be comparable to experimental data.