Abstract Machining experiments are conducted on samples of Carthage marble at atmospheric pressure and under different hydrostatic pressures using a single PDC cutter. Two different experimental setups were used for the two different types of tests. Variations of cutting forces with depth of cut, rake angle and hydrostatic pressure were investigated experimentally. The effect of hydrostatic pressure on chip formation was studied using the experiments. The difference in cutting forces between cutting a groove into the specimen and cutting a slab was investigated at atmospheric pressure. Cutting forces were found to increase with increasing negative rake angle and hydrostatic pressure. The application of an external hydrostatic pressure was found to assist in chip formation.