The theoretical consideration of energies consumed in metal cutting and the experimental observations on orthogonal light cutting of 4-6 brass lead to the conclusion that the size effect in cutting force can be explained as follows: with the decrease in depth of cut, the specific cutting force increases because of
(1) decrease in magnitude of shear angle
(2) the work consumed in the plastic flow of surface layer which is not proportional to depth of cut
(3) decrease in magnitude of real rake angle due to roundness of cutting edge
Considering these facts, the calculated shear stress on the shear plane shows no appreciable variation due to the decrease of depth of cut.