What should a mechanic use to accurately measure the diameter of a hole that is about 1/4 inch?

A small-hole gauge is specifically designed for measuring the diameter of smaller holes, such as one that is approximately 1/4 inch. It has a mechanism to expand to fit the hole and can provide precise measurements by capturing the internal dimensions effectively. This precision is crucial in mechanical applications where tolerances can be tight.

Using a small-hole gauge allows the mechanic to obtain an accurate measurement by inserting the gauge into the hole and then recording the diameter, usually with a comparator or depth micrometer. For holes of this size, the small-hole gauge is more appropriate than other tools.

Other measuring instruments such as large hole gauges, caliper gauges, or micrometers may not provide the same level of accuracy or ease of use for measuring smaller holes. Large hole gauges are better suited for larger diameters, caliper gauges may not fit properly in narrow openings, and micrometers, while precise, typically require a different approach and may be cumbersome for this specific application.