Which instrument uses a calibrated screw to measure small gaps with high precision?

• A. Dial caliper
• B. Vernier caliper
• C. Micrometer
• D. Magnetic base

Answer: (C)

Measuring very small gaps with high precision relies on a mechanism that turns tiny rotational movement into a precise linear shift. A micrometer does exactly that with a calibrated screw. When you rotate its thimble, the spindle moves toward or away from the anvil by a fixed amount per turn because the screw has a known pitch. That means each small rotation advances the spindle by a precise distance, giving readings in very fine increments (thousandths of a millimeter or thousandths of an inch) with repeatable accuracy. This combination of a known screw pitch and direct spindle-to-anvil contact makes it especially suited for high-precision gap measurements.

The other instruments don’t provide that same level of fine, screw-driven precision. A dial caliper and a Vernier caliper use sliding scales and reading mechanisms to infer distance, which are versatile but typically offer lower resolution for very small gaps. A magnetic base is just a mounting accessory, not a measuring instrument.