HSS Twist drill, available from Dormer or Sherwood.
Series J100 – Metric
General purpose drills for steels, cast steel, grey cast iron, malleable cast iron, nickel brass, aluminium alloy and graphite. Point angle: 118°, helix angle: normal, web thickness: standard, relief angle: 10° – 20°, tolerance of diameter: h8, tolerance of shank: f11. Manufactured to BS 328/DIN338RN.
Black Finish (W-Finish)
This is the most common surface finish and is the result of a steam tempering operation in which steam is passed over the product during a controlled tempering cycle, producing a black oxide layer. Black tools are generally recommended for ferrous applications where the oxide layer aids chip flow, helps to dissipate heat by retaining some coolant on the tool surface and also helps to prevent the tool from staining.