Which instrument is used to verify the hole size after drilling?

The Go/NoGo gauge is specifically designed for checking whether a hole meets the specified size criteria after drilling. This type of gauge typically consists of a "Go" side, which must fit through the hole if it is acceptable, and a "NoGo" side, which should not fit if the hole is within tolerance. This ensures that the hole is not only the correct diameter but also fits the intended specifications for further assembly or function in the aerospace context.

Using a Go/NoGo gauge is essential because it provides a fast and efficient method for quality control. The clear pass/fail nature of this gauge eliminates ambiguity, allowing mechanics to quickly ascertain if the hole can be used or if additional rework is required. The other instruments, while also useful in measuring dimensions, do not serve this specific purpose as effectively and often require more detailed measurements rather than a quick verification.