A ring gauge is made from the box end of an authenticated precision threaded member and a plug gauge is made from the pin end thereof. The pin end is machined laterally and radially at its nose to ensure complete engagement of the threads. This piece of copper will become a Bourdon tube, the heart of the gauge. As pressure rises inside the tube, it flexes. This is what will make the indicator needle move when the whole mechanism is assembled. Next comes a brass connector to link the Bourdon tube to an inlet pipe.