What measuring instrument can accurately measure both the depth and diameter of a counterbore?

The dial caliper is an excellent choice for measuring both the depth and diameter of a counterbore due to its versatility and design. It features a sliding scale with a dial that provides precise readings, allowing users to measure internal and external dimensions as well as depths. The jaws of the dial caliper can grip the outer diameter of the counterbore, while the depth rod can extend into the counterbore to measure its depth accurately. This combination of functions makes the dial caliper highly effective for this specific application.

Other instruments, while useful in various measuring tasks, do not offer the same level of convenience or accuracy for both diameter and depth in this context. For example, a vernier caliper could also measure these dimensions effectively, but the dial mechanism of the dial caliper is often easier to read and provides a quicker assessment. Similarly, a micrometer is generally limited to measuring external or internal diameters but not depths with the same efficacy as a dial caliper. A depth gauge, on the other hand, is specifically designed for measuring depth but cannot measure diameter. Thus, the dial caliper stands out as the most suitable tool for measuring both aspects of a counterbore accurately.