Hss step drill bits ideal for precise and fast drilling in thin sheet metal the step drill bit ground from high speed steel is burr free and has nine drilling steps for diameters of 4 to 20 mm suitable for non ferrous metals sheet steel and plastics for drilling in extremely thin sheet metal without pre drilling nine fixed drilling steps 4 6 8 10 12 14 16 18 20 mm without friction deposits lowered shank diameter 10 mm