General description The IRWIN® HSS TCT Tip Drill Bit is designed for precision drilling in various hard materials, including hardened steel, cast iron, bronze alloys, and manganese alloyed steel. Its Tungsten Carbide Tipped (TCT) design ensures durability and efficiency during use. Technical specifications Diameter: 11.5mm Total length: 142mm Working length: 94mm Material: Chrome Vanadium Steel, hardened to 56 Rockwell C Carbide Tip hardness: up to 50 Rockwell C Usage Always use a coolant when drilling with TCT twist drill bits to extend their lifetime. Irwin recommends a 3-6% emulsion as a coolant.