... ISO9001 3 100% virgin tungst Solid carbide step drill,hss & carbide step drills,hss coated step drill GradeCompositionGrain Size(um)Density(g/cm3 ... .838000.6um grain size for the fine-grain cemented carbide, use it to make overall carbide tools, it is the most ... common grade in Type K grade ,which is mainly use to process steel ,cast iron, stainless steel, heat resistant steel ...