Countersink - for metal HSS, of titanium nitride (TIN)
Three fluted countersink. HSS. Surface finish of titanium nitride (TIN) which means significantly reduced cutting forces. TIN-coating also results in a lower co-efficient which in combination for the hardness of the surface finish gives several benefits - longer wear times mean fewer tool changes, less risk of swarf build-up, less motor power results in less effect on tools and machines, which results in less risk of chatter.
Other countersink angles quoted on request.