Starrett 73B-12 Spring Nut Inside Spring Callipers, Steel, 0"/0 mm - 6"/150 mm Range

The Starrett 73B-12 “Yankee” spring-type inside calliper opens to 12” (300 mm) with sturdy construction and smooth action. It is made of flat stock, high-grade steel, for easily reproducible and accurate transfer of measurements of the internal size of an object. This calliper has flat, outward curving legs for inside measurements and comes with a solid nut. Bow spring is flexible yet strong, for reliability. The durable legs are made of flat stock, high-grade steel for long life. The centrally located adjustment rod ensures smooth action when opening and closing the calliper. The hardened fulcrum stud is strong to help prevent give or play in the measurement, which would reduce accuracy. Callipers measure the distance between two opposing sides of an object. They make inside, outside, depth or step measurements, according to their type. Callipers are commonly used in architecture, metalworking, mechanical engineering, machining, manufacturing, carpentry and medicine. The simplest callipers have two legs to mark the two points and require a ruler to take the measurement. More complex callipers use two sets of jaws instead of legs and have up to two graduated scales. Vernier, dial and digital callipers give direct and accurate readings and are functionally identical, having a calibrated scale with a fixed jaw and another jaw with a movable pointer that slides along the scale. The Vernier calliper has a scale sliding parallel to the main scale for an additional, fractional reading to improve measurement precision. The dial calliper has a circular dial with a pointer on a toothed gear rack replacing the second Vernier scale. As with the Vernier, this second measurement is added to the reading from the main scale to obtain the result. The dial calliper is used also for measuring size differential between two objects.