... high efficiency. 2. Uniform surface finish. 3. Reduces machine down time. Solid CBN insert TNMA160408, Machining harden steel ... 64 and so on! Harden steel with HRC50-67, Cutting speed, 50-150 m/min; Feed, 0.05- ... 0.12 mm/rev; Cutting deepth, about 0.2mm General gray cast iron with ... Cutting speed, 50-100 m/min; Feed, 0.1-0.3 mm/rev, Cutting deepth, about 2.5mm CBN inserts for cutting ...