Which tools are used to measure the inside diameter of a cylinder?

• A. Telescoping gauge and micrometer caliper
• B. Dial bore gauge
• C. Micrometer only
• D. Vernier caliper

Answer: (A)

Measuring an inside diameter requires a way to reach and contact the bore walls and then read that contact with a precise external scale. A telescoping gauge is used to span the bore and lock at the size that fits the interior surface. Once removed, the gauge’s width is measured with a micrometer caliper, giving a precise inside-diameter reading. This combination leverages the telescoping gauge’s ability to adapt to any bore and the micrometer’s high precision for the final measurement.

A dial bore gauge can measure bores directly, but the most common and dependable method in many situations is to use the transfer approach with a telescoping gauge and a micrometer. A micrometer alone can’t reach or measure the inside surface, and a vernier caliper isn’t as precise for bore measurements.