The diameter of a bore may be checked accurately and easily with

• A. A Outside Micrometer
• B. An Inside Micrometer
• C. A Caliper
• D. A Depth Micrometer

Answer: (B)

Measuring an internal diameter requires a tool that can fit inside the bore and measure the distance between its walls with precision. An inside micrometer does exactly that: it is inserted into the bore and the measuring anvils move toward the bore walls until they contact, and the reading on the sleeve and thimble gives the bore diameter to a tight tolerance. This setup provides high accuracy and is well-suited for bore work, making it more reliable for internal measurements than other tools. An outside micrometer can’t reach inside the bore, a depth micrometer measures depth rather than diameter, and a caliper can measure internal distances but is typically less precise due to jaw alignment and parallax, especially in narrow or deep bores.