Go/No-Go Gauge

A go/no-go gauge is a manufacturing inspection tool that checks whether a machined part falls within its specified tolerance range without producing an exact measurement, returning only a pass or fail result. One end or feature of the gauge, the go side, is sized to the maximum acceptable material condition and must fit or engage the part; the other, the no-go side, is sized to the minimum acceptable condition and must not fit. The tools commonly take the form of plug gauges inserted into holes or threads, pin gauges for small bores, and snap gauges with paired jaws that check an external dimension in a single motion. Because they require little operator skill, tolerate rough factory conditions, and check quickly, go/no-go gauges became a standard fixture of interchangeable-parts manufacturing, verifying at high volume that parts from different machines, or even different factories, will actually fit together.