Suitable for alloyed and non alloyed steel up to a tensile strength of 1000 nmm stainless steel v2av4a cast iron cast steel acid and heat resistant steels precision drill bits that are resistant to heat and wear for use in drill stands or in pillar drills the hss co drill bits are available in two qualities the topline drill bits are for the highest requirements and the standard drill bits are for professional use 6 piece robust line metal drill bit set hss co din 338 135 2