Abstract— Sintered Tungsten Carbides with 25wt% Co are commonly applied for the die and molds of the metal forming process because of their high hardness and wear resistance compared with alloy steel. Cubic Boron Nitride (CBN) is a cutting tool material effectively used to machine the dies and molds made from the sintered tungsten carbide 25wt%. Also, the surface roughness is a fundamental parameter for determining the accuracy and quality of dies and molds. In this study, Face Central Composition Design (FCCD) was selected to investigate the influences of the machining parameters on surface roughness Ra and optimize the cutting conditions. The results showed that feed rate was the strongest factor affecting surface roughness. The model for surface roughness based on the cutting parameters (depth, cutting speed, and feed rate) is formulated. Moreover, surface roughness reaches the minimum value of 0.08 μm at the cutting speed of 55 m/min, feed rate of 0.1 mm/rev, and cutting depth of 0.19 mm.