Under atmospheric conditions rock cutting is mostly brittle; either based on tensile cracks or based on shear cracks, although ductile cutting is possible. It is known from the drilling industry that under very high hydrostatic pressures often a sort of ductile cutting process occurs. Cutting under very high hydrostatic pressures is called hyperbaric cutting. Combining the cutting theory of water saturated sand of Miedema and the classic rock cutting theory of Merchant, the 2M theory, results in a new application of the theory for hyperbaric rock cutting. The new theory contains the pore pressure and the cohesive terms. To verify this theory the measurements of Zijsling (1987) are used, which go up to pressures of 1000 bar. A complication is that the chips cut will start to curl, but the contact length of the chip cut with the blade is unknown. Using the equilibrium of moment’s, results in a method for determining this contact length. In the specific case a contact length of about 4–5 times the layer thickness is found, resulting in an almost perfect match with the measurements. The paper shows the measurements and the theory.