Abstract: A boring bar has a shank having a cutter support head at one end. A flow passage extends longitudinally through the shank to the cutter support head and intersects a transverse flow passage that is defined in part by a clamp screw passage of the head. A metal cutting insert is clamped to the cutter support head by a clamp that is secured by a clamp screw being threaded into the clamp screw passage. The clamp member defines at least one coolant fluid flow passage having a discharge opening or openings each located and oriented to direct a jet of coolant fluid onto the metal cutting insert immediately at the site of cutting engagement within the rotating workpiece. The clamp screw defines an internal passage that communicates with the transverse coolant fluid flow passage and conducts coolant fluid onto the metal cutting insert.