Abstract: An improved manufacturing method produces small orifices in a succession of work pieces according to a desired flow specification. After the work pieces are subjected to one or more preliminary processing steps, an apparatus, preferably an electro discharge machine, is used to produce a small orifice in each work piece. A gas, preferably nitrogen, is flowed through the orifice produced in a work piece, and the pressure drop of the gas flowing through the orifice is measured, preferably by a pressure gauge capable of providing both a visual display for a human operator and an electrical signal for a microprocessor. The pressure drop is compared to a correlation of pressure drop and the desired flow specification. The results of the comparison are used to determine whether an adjustment is needed to the apparatus and/or one of the preliminary processing steps.