Flute countersink and deburring tools. Straight shank, CNC precision cam ground, M35 cobalt steel material, chatter-free cutting action. Made in Great Britain. Set includes 100 degree 5/16", 3/8", 1/2", 5/8" head diameter countersink. Cobalt steel tools are similar to high-speed steel, but with more cobalt for improved performance when cutting harder metals such as stainless steel or nickel alloys. Uncoated tools feature just the base substrate without any additional treatment or coatings and are suitable for a wide range of applications. 100 degree angle.