Slide caliper for measuring thread diameters - uses split circular jaws which are adjusted by vernier slider

摘要

The instrument for measuring internal and external screw threads consists of a slide-rule type of caliper with one fixed and one moving arm (4, 5). Each arm has attached to it a plate (1) having two semicircular openings in line (2, 3). The plates form a pair of jaws between which the screw-threaded component may be inserted. The jaw separation is adjusted by a vernier slider (11) which moves along the fixed, calibrated handle of the caliper. The graduations are provided on either side of the rule so that a range of diameters may be catered for without increasing the length of the handle. The diameters of the circular openings in the jaw plates are machined to 'go' and 'no-go' diameters (2, 3).