The Starrett 424 pocket slide caliper has a 0 to 3.5" measuring range with 0.03125" graduations for gaging wire and drill rod. The 1.375" jaw depth tests United States Steel Wire Gage sizes 0 through 36 and decimal equivalents are engraved on the gauge back side. The hardened stainless-steel frame and slide are durable and corrosion resistant.
Calipers measure the distance between two opposing sides of an object. They make inside, outside, depth, or step measurements, according to their type. Calipers are commonly used in architecture, metalworking, mechanical engineering, and machining. The simplest calipers have two legs to mark the two points and require a ruler to take the measurement. More complex calipers use two sets of jaws instead of legs and have up to two graduated scales. Vernier, dial, and digital calipers 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 caliper has a scale sliding parallel to the main scale for an additional, fractional reading to improve measurement precision. The dial caliper 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 digital caliper takes a differential by zeroing the display at any point along the slide, with an LCD that displays a single value in English and/or metric units.
The L.S. Starrett Company manufactures precision measuring tools, metrology and testing equipment, and saw blade products. The company, founded in 1880, is headquartered in Athol, MA.