9 SOLID HSS MILLS – TOOL MATERIALS NAVIGATOR Tool materials High Speed Steel A medium-alloyed high speed steel that has good machinability and good performance. HSS exhibits hardness, toughness and wearresistance characteristics that make it attractive in a wide range of applications, for example in drills and taps. Cobalt High Speed Steel This high speed steel contains cobalt for increased hot hardness. The composition of HSCo is a good combination of toughness andhardness. It has good machinability and good wear resistance, which makes it usable for drills, taps, milling cutters and reamers. Cobalt Powder Sintered Cobalt High Speed Steel (HSCo powder metal) is a substrate produced using powder metallurgy technology. Tools using Metallurgy Steel substrates produced by this method exhibit superior toughness and grindability. 118