Work 5 of cylindrical shape, to be checked, is placed over the outer end of plug 1. Ball 2, actuated by spring 3, locates the work against the outer surface of plug 1. Nozzle a in the plug is connected by channels to connection 4. Second nozzle d is provided in the body of the gauge. The wall of work 5 being checked is confined between the two nozzles to which compressed air is delivered through connection 4 from a back-pressure gauging system. According to the clearances between the nozzles and the wall, a pressure, measured by a manometer, is established in the gauging system. This indicates the wall thickness. Work 5 is turned about the axis of plug 2 to determine the differences in thickness of the wall and, consequently, the lack of concentricity of the internal and external surfaces of work 5.
$3707$SHP,M$