Abstract: A high pressure liquid jet abrasive cutting apparatus having a removable and replaceable cartridge assembly. This cartridge assembly has a nozzle unit with a jewel orifice, an intermediate mixing chamber where the liquid jet and the abrasive particles mix, and a discharge tube through which the liquid jet incorporating abrasive particles therein is discharged. The nozzle unit and the discharge tube are preassembled in a cartridge housing at a factory location under controlled conditions, so that precise alignment is obtained. Replacement of the worn parts is accomplished by interchange of the cartridge assembly.