A twist drill assembly (10) comprising a shaft (30) and a drill tip (20); the shaft having a single internal shaft conduit (34) for a fluid, extending between orifices (36, 37) formed into the shaft; the drill tip having an internal drill tip conduit (22) for the fluid, extending between orifices formed into the drill tip; the shaft and the drill tip configured such that the drill tip is connectable to an end of the shaft with the internal drill tip conduit in communication with the internal shaft conduit, allowing the fluid to be capable of flowing from the internal shaft conduit into the internal drill tip conduit; the internal shaft conduit having a spiral form aligned with a central longitudinal axis of the shaft, and configured to complement the arrangement of spiral flutes (38) formed on the shaft.