What tool would you use to measure small holes?

• A. Caliper
• B. Telescoping gauge
• C. Bore gauge
• D. Depth gauge

Answer: (B)

Measuring the inside diameter of a hole requires a tool that can reach into the bore and establish an accurate interior span to transfer to a known reference. A telescoping gauge does exactly this: you insert it collapsed, expand it until its segments contact the bore walls, then lock it in place. When you remove it, you measure the gauge's outside dimension with a micrometer (or caliper) to yield the hole’s diameter. This approach is especially handy for small or hard-to-reach holes where direct inside-reading tools aren’t practical.

Compared to a depth gauge, which measures depth rather than width, or a caliper, which may not fit into tight bores, or a bore gauge, which is great for bores but often less flexible across a range of small sizes, the telescoping gauge provides a reliable way to capture the inside dimension first and then obtain the precise measurement with a standard instrument.