The key element in water jet machining is a water jet, which travels at velocities as high as 900 m/sec (approximately Mach 3). When the stream strikes a workpiece surface, the erosive force of water removes the material rapidly. One of the most crucial elements is the nozzle, in which water pressure is transformed into high velocity water jet and thus need proper design. Water jet machining is applied in various industrial areas ranging from cleaning, deburring and cutting of titanium in aerospace industries. It is also widely used for the machining of fibre reinforced plastics .