Which instrument measures external dimensions with moderate accuracy, such as bolt size?

Which instrument measures external dimensions with moderate accuracy, such as bolt size?

• A. Caliper
• B. Micrometer
• C. Ruler
• D. Tape measure

Answer: (A)

Measuring external dimensions with a practical level of precision requires an instrument that can clamp around the outside of the part and display a readable measurement. A caliper does exactly that: its outside jaws grip the bolt or similar object and give a reading in inches or millimeters with enough accuracy for everyday hardware work. It’s fast, versatile, and covers a reasonable range, making it ideal for identifying bolt size. Ruler and tape measure lack the necessary precision for typical bolt measurements, especially for diameter. A micrometer offers higher precision but is aimed at very small features and specific dimensions; it’s less convenient for a range of bolt sizes and larger parts.

Measuring external dimensions with a practical level of precision requires an instrument that can clamp around the outside of the part and display a readable measurement. A caliper does exactly that: its outside jaws grip the bolt or similar object and give a reading in inches or millimeters with enough accuracy for everyday hardware work. It’s fast, versatile, and covers a reasonable range, making it ideal for identifying bolt size.

Ruler and tape measure lack the necessary precision for typical bolt measurements, especially for diameter. A micrometer offers higher precision but is aimed at very small features and specific dimensions; it’s less convenient for a range of bolt sizes and larger parts.