Water jet machining is a new cutting method that ultra high-pressure water with a maximum pressure level of 392 MPa is jetted from the small-diameter jet nozzle ata speed approximately 3 times faster than the speed of sound and this water jet is made incontact with a workpiece to cut it.

Two kinds of cutting methods with utlization of water jet are provided, one is "Water Jet Cutter" that only water is pressurized to an ultra high-pressure water to improve the machining capability and this high-pressure water is jetted.