If the no-go ring gauge does not fit over the outer diameter of the part, then this indicates that the minimum allowable material condition for the part has been satisfied, meaning that the diameter of the part exceeds the minimum or lower limit of its tolerance, and therefore, the part is acceptable. No-go ring gauges check the lower tolerance limit on the outer diameter of the part. If the go ring gauge fits over the outer diameter of the part, then this indicates that the maximum allowable material condition for that part has not been exceeded, meaning that the diameter of the part falls within the upper limit of its tolerance, and therefore, the part is acceptable.

Go ring gauges are designed to verify the upper tolerance limit of the outer diameter of the part. There are three primary types of ring gauges from the functional perspective: To learn more about the other varieties of gauges, see our related guide covering the different types of gauges. These types of gauges are not addressed in this article. Note that there is an alternative context of the phrase ring gauge which is used in the jewelry industry and refers to tools (also called ring mandrels) that are used to gauge the sizes of rings such as wedding bands. This article will provide information about the types of ring gauges, the various configurations that exist, the tolerance sizes, and the uses of these instruments. It is not a measurement instrument in the sense that it is not providing an actual value of the part’s diameter – it simple gages whether the part falls within permissible limits and therefore can be accepted from a quality control perspective. It important to note that ring gauges are used to quickly establish if a part falls within the accepted tolerances and yields a yes/no condition based on the gaging. The use of ring gauges enables inspections and quality decisions about machined parts to be made very quickly without the need to resort to the use of micrometers, calipers, thickness gauges, or other measurement instruments that could take longer to yield a result. The primary function of ring gauges is to establish on a go/no-go basis whether the part being gaged falls within the dimensional tolerance that was specified for it. These gauges are typically cylindrical in shape and are fabricated from a stable material (usually tool steel) with a highly precise (very high-tolerance) bore in their center that functions as the gauge for the outer diameter of the parts. Ring gauges are metrology tools that are used for gaging the outer diameters of pins, shafts, splines, fasteners, dowels, studs, and other machined cylindrical parts. A thread ring gauge used for checking threaded parts.

Ring gag harness