Abstract
This pneumatic divice makes use of the variation in total resistance of a compressed gas leaving from two symmetrical orifices which are at an equal short distance (h) from the wall (its diameter D) of a workpiece to be measured. It is arranged so that the compressed air with constant initial pressure (PA), passing through the fixed orifice, may part into two branches to jet out of two measuring orifices, and that the pressure of the air in the space between the fixed orifice and the branching point can be measured. The nondimensional amplification |dPC/dD| (dB/PA). (dB/d2) and the suitable clearance (h/dB).(d2/dB) are respectively represented theoretically as the functions of a characteristic parameter (dynamic similarity factor) consisting of Reynolds Number, d2/d1 and dB/d2 The results thus obtained fairly agree with those of the experiment. When two jetting clearances are not equal, errors in comparative checkingwhich are small in comparing with the symmetrically standard characteristics will appear. Such errors, however, can be eliminated only by keeping two jets with guide pieces, contacting very closely to the works, horizontal. We can plan through the rtsults obtained the checking of ID by air spindles, OD by air rings and thickness of plastics and foils by air snaps with any desirable sensitivity.
