A cast metal plate segment for a refiner of lignocellulosic material or a disperser of comminuted paper or packaging products, the plate segment including a front side with a front surface configured to refine the lignocellulosic material or disperge the comminuted paper or packaging products, and a back side, opposite to the front side, including a corner or edge, wherein the corner or edge comprises a casted surface between machined planar surfaces adjacent the corner or edge.