Starrett 50A Trammel Heads With Divider Points And Pencil Socket, 3" And 2-1/2" Point Size

The Starrett 50A improved trammel heads with adjustable divider points (2-1/2” and 3” size) and pencil socket measure the distance between any two points that are too far apart to be reached with dividers. The heads are die cast with black wrinkle finish and have hardened, forged steel points, for easily reproducible and accurate transfer of measurements, scribing lines, arcs and circles and marking distances between two points. The heads accommodate a beam up to 3/8” (9.5 mm) thick and 3/4” (19 mm) wide. 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.