The idea of cutting with water might be as old as the Chinese phrase "dripping water penetrates rock." In modern waterjet technology, the "dripping water" is replaced by a high velocity water stream that penetrates rock in seconds. The early stage nozzle was crude and unreliable, and so abrasive waterjet was thought to be a very imprecise process. Waterjet abrasive technology was used only when other technologies could not handle the job. The precision and user-friendliness achieved through better nozzle and control technology has changed people's perspectives about this technology.

An abrasive waterjet is formed by entraining abrasive particles into a high velocity water stream. The essence of abrasive waterjet machining is rapid erosion combined with rapid cooling. In most cases, water does not participate in material removal, but serves as an energy carrier and a flushing medium. Bulk material removal is the result of accumulated micro-cutting effects of individual abrasive particles as in conventional grinding. The individual abrasive particle simply digs into the material and scoops out a small piece. Some of the abrasive particles may even strike the material a second or a third time.

A typical Abrasive Water Jet machine is composed of a high-pressure pump, motion equipment and control, nozzle and abrasive system, a working table, and a waste collecting unit. A typical layout is shown:

Two types of high-pressure pumps are currently available in the industry: intensifier pumps and crank drive pumps. Intensifier and crank drive pumps share the same pumping principle. In both, a plunger is pushed into a closed chamber, which raises the pressure and expels the pumped fluid through an outlet check valve. Then, the direction of the plunger motion is reversed and low-pressure fluid fills the chamber through an inlet check valve. The continuously reciprocating plunger provides the pumping action. The difference between the two technologies is simply the means by which the plunger is moved. The crank pump uses a crank similar to the one in an automobile engine. The intensifier drives the plunger by hydraulic cylinder, usually with oil. Cranks are moving into high pressure service because they are simpler, much more efficient, and cost less.

Waterjets are capable of cutting many industrial materials including mild steel, stainless steel, titanium, aluminum, tool steel, ceramics, granite & marble, glass, foam & rubber, Gasket, brass, copper, wood and armour plate.

The motion equipment for AWJs is similar to the equipment used for laser and wire EDM. A typical AWJ machine tool includes a precision X-Y axis rigidly mounted to the cutting table, pre-loaded linear bearings, and precision ball screws. The motion track has complete protection against water, dirt, and grit. Special damping mechanisms are also used to achieve smoother motion. The X and Y axes are driven by brushless servo motors, which are controlled with a CNC controller. Today's PC controls for abrasive jetting incorporate a model of the cutting process and drive the machine at exact speeds at every point of the path, achieving the requested cut quality. The machine automatically speeds and slows for corners and other features of the geometry, realizing maximum precision. Moreover, this type of control performs the calculations with such rapidity and accuracy that it is possible to make single parts to high precision with about the same effort required to plot a drawing on paper.

An orifice, typically made out of sapphire or diamond, is used to convert the potential energy of high pressure water into the kinetic energy of a high velocity water stream.

The downstream section is constructed to be like an air ejector. It includes a suction chamber and a converging nozzle. The water stream entrains air in the suction chamber, and the mixture discharges from the converging nozzle. This builds vacuum pressure in the suction chamber, which allows entraining abrasive particles. The suction chamber and the converging nozzle are therefore often called the "mixing chamber" and the "mixing tube," respectively.

The abrasive waterjet discharging from the mixing tube is actually a mixture of abrasive, water, and air. While air helps in the entraining of the abrasive, it has no contribution in material removal, and it brings in a negative effect by dispersing the jet. A well-designed nozzle minimizes air flow.

The working table is where a workpiece is placed and fixed. A steel grid is often used to support the workpiece. Since the machining force is minimal, a simple clamping device or even a weight is sufficient to hold the workpiece in place. Underneath the working table is a waste collecting tank. To reduce noise level, the tank is filled with water so that cutting can take place while submerged. In some cases, used abrasive is processed through a recycling unit and some is reused.