For the production of high precision concentrically centred countersinks in most metals where pilot holes have been pre-drilled. Shank diameter: 3/16" Inclined Angles for Countersunk Socket Head Screws Thread Series: Metric. Standard: BS EN ISO 10642. Thread Size: up to M20. Countersink Angle: 90. Thread Series: Metric. Standard: BS EN ISO 10642. Thread Size: over M20. Countersink Angle: 60. Thread Series: UNC/F. Standard: ANSI B 18.3. Thread Size: No.0 to 1". Countersink Angle: 82. Thread Series: BSW/F. Standard: BS 2470. Thread Size: 1/8" to 1". Countersink Angle: 90. Thread Series: BA. Standard: BS 2470. Thread Size: 8BA to 0BA. Countersink Angle: 90.