With special surface treatment GOLD-TECH + FULLY GROUND + special steel HSS-XE are ideal for drilling in steel up to a strength of 40 Rockwell (HRC) and even suitable for stainless steels. Only a few manufacturers are capable of producing step-hardened annular cutters. For Karnasch this is “standard”. This allows to us produce extremely hard tooth tips (68 HRC) and yet a flexible annular cutter.