HSS blue ring ISO (BLT) metric coarse oxidised spiral flute taps are made with a strong high speed steel with a black oxide finish for deep blind holes with reduced wear and improved heat resistance. Features and Benefits • High speed steel construction • Black oxide finish for reduced wear and improved heat resistance Specification • For deep blind holes • Helix angle 45° • BTL - Biteless taper • Taper lead to DIN form C (2 x P to 3 x P) • Tapping tolerance to 6H • DIN 371/376 Typical Applications • Tapping • Steel • Stainless steel • Cast iron