firm-joint caliper

Firm-joint calipers are a type of measuring instrument with two adjustable legs or jaws used to determine the dimensions of objects. Unlike spring calipers, which use a screw and nut for adjustment, firm-joint calipers rely on friction at the joint to maintain their position.1

These calipers come in two main forms:
* Outside calipers: Used to measure the thickness and outside diameters of objects.1
* Inside calipers: Used to measure the diameters of holes and the distances between surfaces.1

Accuracy with firm-joint calipers largely depends on the operator's sense of touch. A hermaphrodite caliper, a variation, features one inward-bent leg and one straight leg with a sharp point, used for scribing lines at a set distance from a surface.1