Toolwear and surface roughness in milling of die steel using binderless CBN end mill

In this study, the authors describe the cutting characteristics of binderless CBN end mills in milling of die steel. A single flute radius end mill having a diameter of 0.5 mm and corner radius of 0.02 mm was in the experiment. Heat-treated steel, stainless steel, and high-speed tool steel were cut using a high-speed spindle, allowing for the analyses of tool wear and surface roughness. The results revealed that the wear volume increased with an increase in the hardness of the work material although the edge retreat amount after cutting 25 m was less than 5 μm. The average surface roughness of the finished surface was less than 15 nm in all the work materials. A mirror-finished surface was also obtained. This result contributes to the automation of the polishing process of metal molds and to the more efficient use of labor.