What tool is used to inspect the depth of a countersink?

The correct tool used to inspect the depth of a countersink is a Federal gauge. This specialized instrument is specifically designed to measure the depth of countersunk holes accurately. It has a depth measurement feature that allows for precise readings of the countersink depth, ensuring that it meets the required specifications for aerospace assembly.

Depth gauges, while useful for a variety of depth measurements, do not provide the same level of specificity for countersinks as a Federal gauge. Calipers and micrometers, although they can measure dimensions, are not typically used for countersink depth due to their design, which is not tailored for that specific application. Thus, the Federal gauge stands out as the most appropriate tool for this task.