Evaluating Ash: lf and ef(x′ )
Expressions for lf and ef(x′) are simplified by the assumption that the effective shear plane angle fe is a constant, the same on every cutting velocity–chip velocity plane, for given cutting conditions. In terms of the effective uncut chip thickness t1e (Figure 6.14(b)),
he projected infinitesimal cutting edge length dS′ in the x′–y′ plane: