4.00MM HSS-Co 8% 3 Flute Threaded Shank Slot Drills - Uncoated. Centre cutting. Threaded shank to DIN 1835B. Uncoated (for general production machining) TiCN Coated (extends cutter life and improves work material surface finish) and TiALN Coated (dissipates and resists heat, reduces surface friction coupled with high surface hardness).