Method and apparatus for simultaneously forming a plurality of openings through a substrate

An improved method and apparatus for abrasive jet machining. A special spray nozzle unit is provided which is mounted within a cavity in a retaining block. Each nozzle unit is preferably made of multiple components secured together within the cavity. Also, such unit includes at least two passageways therethrough. In a preferred embodiment, the unit is divided into two heads, each head being substantially triangular with a flattened apex. The retaining block has at least one port therethrough which communicates with the passageways in the heads. A flow of particulate materials into the block passes through the passageways in the heads, simultaneously producing multiple particulate streams. The multiple streams may then be directed toward a substrate in order to simultaneously produce a plurality of openings through the substrate.