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The air ring has a precision ground hardened steel body with built-in air gage nozzles. When the ring is slipped over the workpiece, the resulting back pressure is sensed by the air gage readout and displayed as the diameter of the part. Air rings come in 2 and 3-jet configurations. The 3-jet air ring checks for 3-lobe out-of-round conditions prevalent in centerless ground parts that can not be detected with a 2-point gage.
Air ring styles Center-jet style air rings have gaging nozzles in the center of the body; shoulder type have the nozzles near the edge.
