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

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

• A. Small hole gauge and a micrometer caliper.
• B. Vernier caliper and depth micrometer.
• C. Dial indicator and outside micrometer.
• D. Inside micrometer and radius gauge.

Answer: (A)

To measure the inside diameter of a small hole, you need a tool that can reach inside and contact the bore, plus a precise reader to determine the size. A small hole gauge is inserted into the hole and expanded until it just fits the bore; then you withdraw the gauge and measure its span with a micrometer caliper. The micrometer’s reading gives the hole’s inside diameter. Other options don’t provide the correct combination: they either measure outside dimensions, measure depth, or measure radii rather than the actual internal diameter.

To measure the inside diameter of a small hole, you need a tool that can reach inside and contact the bore, plus a precise reader to determine the size. A small hole gauge is inserted into the hole and expanded until it just fits the bore; then you withdraw the gauge and measure its span with a micrometer caliper. The micrometer’s reading gives the hole’s inside diameter. Other options don’t provide the correct combination: they either measure outside dimensions, measure depth, or measure radii rather than the actual internal diameter.