A cutting tool has an internal cutting tool fluid delivery system. The cutting tool has a tool body and a fluid delivery head coupled thereto by a solid coupling member with a continuous male thread. The tool body includes a body coupling bore and the head includes a head coupling bore which communicates with the body coupling bore. At least one of the body and head coupling bores includes a circumferentially interrupted female thread which has a longitudinal thread axis and a radial outer thread boundary. The or each coupling bore having the female thread includes a thread passage which extends along the thread axis. In an axial cross section of the female thread, the thread passage extends both inside and outside the radial outer thread boundary.