... .Double Tempering- Temperature (2 hrs minimum) 250°C, better toughness.(58-59HRC).- Temperature (2 hrs minimum) ... thread cutting tools, chasers, cold forming tools, arbors, drill bushings, collets, drawing punches, machine knives for the wood, paper ... - 820 °CQuenching media : Oil, Salt bath ( 200 - 250 °C )Hardness after quenching : 63 - 65 HRCHardness after tempering : Tempering °C100200300400HRC64625852 ...