Apparatus for generating a high-pressure fluid jet

An improved apparatus for generating a high-pressure fluid jet includes an orifice mount (11) having a frusto-conical surface (12) that engages a frusto-conical wall in a cutting head (22), the geometry of the orifice mount (11) and cutting head (22) being selected to increase the stability of the mount and reduce deflection of the mount adjacent a jewel orifice (20), when subjected to pressure. Alignment of a nozzle body (37) and the cutting head (22) is improved by providing pilot diameters both upstream and downstream of threads on the nozzle body (37) and bore (23) of the cutting head, respectively. Accurate placement of a mixing tube (49) in a cutting head is achieved by rigidly fixing a collar (52) to an outer surface of the mixing tube (49), the collar engaging a shoulder (34) and bore of the cutting head downstream of a mixing chamber (33), to precisely locate the mixing chamber (33) axially and radially.