Inside and Outside Diameters Air gages are most commonly used for measuring the size and form of inside diameters (IDs) and outside diameters (ODs). Two-nozzle air plugs, with nozzles diametrically opposed, are often used for internal measuring, and two-nozzle air rings are used for external dimensions.
Averaging Multiple nozzles are equally located about the circumference of the air tool to allow for average size measurement. Commonly used for thin-walled or out-of-round parts – four, six, or more nozzles are used, depending on the tool size.
Out-of-Round Air tools can gage a part for roundness. For two-point out-of-round conditions, a standard two-nozzle air tool can be used. If lobing exists in the part, an odd number of nozzles must be used, depending on the number of lobes.
Straightness A common application of air gaging is to dynamically measure the straightness or "bow" of an ID. In this case, a custom-designed air plug makes verifying a part's straightness simple and fast. (A straightness air plug cannot measure diameter).
Squareness To determine squareness of a part, for example a bore to face, air nozzles configured as a "z" are used with dynamic measurement to change the back pressure from square to out-of-square conditions.
Taper Angle variation of tapered surfaces is commonly checked with air gaging as the difference of two diameters.
Flatness To measure flatness, an air nozzle is mounted within a stationary platen. The part is then moved across the nozzle. This process provides a convenient, quick method to accurately gage flatness.
Groove Width The measurement of grooves is conveniently achieved with flat, blade-type air tools. Air gaging not only determines groove size, but with exploration around the workpiece, parallelism of the groove faces can also be determined.
Matching A specified clearance between two mating parts is often required to assure proper part operation. An amplifier allows for the individual display of the bore size, the shaft size, and the clearance between the two parts. Operators need only observe the clearance display to determine if the two components have the required match dimension.