Callipers for large forgings possess handles, and are denoted by Figs. 243, 244, and 245. The tool shown by Fig. 243 has a hole at one end to allow the tool to be hung in a safe place, after being adjusted, and when not required for immediate use. The handle may consist of iron, and be distinct from the callipers, that are of steel; or the handle may be an extension or continuation of one of the calliper legs, in which case the entire tool is of steel.

Fig. 244 indicates a couple of outside callipers attached to one connecting-rod. This rod is long enough to allow the workman to measure the work without being scorched; and one of the callipers should be smaller than the other, because when both callipers are adjusted to two different dimensions, the smaller callipers should be for the smaller dimension; consequently, the workman will not be so liable to put the small callipers to the work when he ought to put the large one; such a mistake causes him to reduce the work more than necessary, and obliges him to afterwards upset it to the proper size.

By thus adjusting two pairs of callipers, or, properly speaking, two callipers, two dimensions of a forging are easily reserved by keeping the callipers adjusted until the forging is reduced to the two dimensions. Such callipers are useful for measuring the large and small ends of cones, the large and small parts of bolts and rods, also the lengths and widths of T-ends. A connecting-rod callipers in use for T-ends is represented by Fig. 200.

Fig. 245 denotes two callipers of another class, named inside callipers, which are for measuring two holes of different diameters, or for measuring one hole of two different diameters. Inside callipers measure also the large end and the small end of a conical hole; also all such openings as slots, gaps, grooves, and key ways.

The joint-pins of all such callipers should be tightly riveted until the legs cannot be shifted without a considerable strain being applied; this tightness being necessary to prevent the legs shifting when not desired. During the adjustment of such cllipers,it is proper to separate or close the legs until the points are about an eighth of an inch further from each other than required to be when adjusted. After this, the feet or points are closed to the proper distance with a few blows of a hammer. To do this conveniently, the callipers are put upon some convenient piece of soft iron or other metal, with the edges of the legs upwards, and one edge resting on the iron ; while in this position, the point or toe of the upper foot is gently hammered with a smooth-faced hammer, or a copper hammer, until the feet or points are at a proper distance from each other. After one callipers are thus adjusted, the other callipers at the opposite end of the rod are adjusted by similar means. This mode of adjusting, by hammering the callipers, instead of using the callipers as a hammer, prevents the adjusted callipers being shifted while the other callipers are being adjusted.