Compressed air is delivered through the restrictor into the measuring chamber of a back-pressure gauging system and then passes through channel a to four measuring orifices d arranged in pairs at the opposite threads of gauging plug 1. The outlets d of the orifices are at the middle of the thread profiles. The provision of four orifice outlets keeps the measured results independent of displacements of the plug in the radial and axial directions. The pressure gauge of the system indicates the magnitude of the clearance between the gauging plug and internal thread being checked at the points where the measuring orifices are located.
$3705$SHP,M$