An experimental technique had been developed for studying cutting with single tools of known geometry at very small depths of cut. It has been shown that the specific cutting energy decreases as the thickness of the cut is decreased, a result which is contrary to that obtained in previous investigations with grinding wheels and to that expected from consideration of the influence of specimen size on the yield value of shear stress. These apparent anomalies are discussed in terms of the width of cut and the size of the plastic zone.