dialcaliper

A dial caliper is a precision measuring instrument used to determine external dimensions, internal bores, and depths. It comprises a rigid beam with a fixed jaw and a movable jaw, a dial indicator driven by a rack and pinion, and often a depth-rod. The dial provides a continuous readout of the sliding jaw position.

To take a measurement, the object is placed against the jaws and the sliding jaw is moved until contact is made. The main scale shows the nominal units, while the dial indicates the fraction of those units. Operators may zero the dial at any reference position to measure relative changes.

Dial calipers are typically less expensive than digital calipers and do not require a power source. They offer quick, intuitive readings and are robust in workshop environments, but can be susceptible to parallax error and wear of the rack and pinion. Readouts are usually in thousandths of an inch or hundredths of a millimeter, depending on the model.

Common applications include machinist work, automotive, and metal fabrication, for checking parts, setting tolerances, and inspecting batches. They come in metric and imperial versions and with different jaw designs for external, internal, and depth measurements.

Maintenance involves keeping the instrument clean and dry, regular zero checks, and occasional lubrication of sliding surfaces. Proper storage in a protective case protects against dust and impact. Dial calipers contrast with vernier and digital calipers by providing an analog dial readout and no battery dependency.