Callipers

Instruments used for measuring diameters of rods and cylinders in machinists' work. The ordinary ones are like a pair of dividers with the legs curved outward, so that the points may touch the work at opposite ends of a diameter. The distance between the points can then be measured by a scale. Callipers. 30° 20° For exact work and manufacturing in quantities, GAUGES (q.v.), are often used instead. These may be standard gauges or simply templates of thin metal. For fine measurements a mi crometer or vernier calliper may be used. These instruments read to the one-thousandth of an inch from a fixed or adjustable zero by the method which their name indicates.