Red Seal Machinist Practice Exam

What measurement tool is best for checking the diameter of a drilled hole?

1. Vernier caliper

2. Bore gauge

3. Micrometer

4. Measuring tape

The correct answer is: Bore gauge

The bore gauge is the most appropriate tool for measuring the diameter of a drilled hole due to its design and functionality. A bore gauge is specifically engineered to evaluate the internal diameters of openings, such as holes, in a precise and efficient manner. It typically consists of a measuring rod with a dial indicator and is capable of providing accurate measurements by fitting into the hole and measuring its width at various points. This specialized nature allows it to take measurements that are more precise than those achievable with more general tools. The bore gauge can accommodate different hole sizes and depths, making it a versatile choice in machining and inspection work. Other tools like the vernier caliper and micrometer can be used for external measurements or for measuring the diameter of small parts but are not as effective for measuring the interior dimensions of drilled holes. A measuring tape also lacks the precision required for such tasks, making it unsuitable for accurate diameter measurements in a machining context. Thus, the bore gauge is the optimal choice for accurately assessing the diameter of drilled holes.