The influence of inhomogeniety of deformation in bulk metal forming processes is analyzed. A modified yield criterion is proposed introducing an inhomogeniety function to take into account the friction and wedge effects. It is found that both interfacial friction and surface angularity can affect the inhomogeniety of deformation and velocity distribution significantly. Increasing friction and wedge effects does not necessarily increase the severity of inhomogeneous deformation. A cancellation effect is observed. Friction factor under sticking condition can be determined applying the no-slip boundary condition to the velocity field equation.