The second operation (illustrated in Fig. 2) is to punch out of the pair of opposite webs, a a, pairs of oblong mortises—two pairs, c c, and one pair, d d. These three pairs of mortises (which might be punched at separate operations, but are preferably punched at one stroke of the press) are situated as close as possible up to the faces of the other pairs of webs, a’ a’, the pairs of mortises, c c, being so spaced as to correspond in position to the eyes of the links to be formed, to which they correspond approximately in form, while the pair, d, correspond in position to the notches, b, and therefore to the intervals by which the links formed out of the same pair of webs, a a, will be separated when completed. This operation is continued along the whole length of the pair of webs, a. It will be observed that a considerable thickness of metal is left at a* between the notches, b, and the mortises, d. This is of primary importance and is one of the essential features of my method of manufacture, inasmuch as by first punching out the mortises, d, the subsequent removal of the metal from between the outer ends of the links is greatly facilitated, while by leaving the solid metal, a*, the transverse strength of the webs, a a, is not materially diminished, so that when the operation of punching the mortises, c and d, in the other pair of webs, a’, is performed the bar will not be bent and crippled, as would inevitably be the case were the whole of the metal opposite the notches, b, which is ultimately to be removed, to be punched out at so early a stage of the manufacture. The operation of punching the pairs of mortises, c’ and d, having been repeated along the other pair of webs, a’, it will be observed that like the notches, b, the mortises, c d, in the one pair of webs alternate with those, c’ d’, in the other pair of webs.
The third operation (illustrated in Fig. 3) is to elongate the mortises, c d, and bring the mortises, c c’, more nearly to the final form. This is performed by punches similar to but larger (in the direction of the length of the rod) than those used in the second operation.
The third operation, which is repeated upon both pairs of webs, a a a’ a’, may be considered as a second stage of the second operation, it being preferable to punch out the mortises in two stages in order to remove sufficient metal without unduly straining the bar.
The fourth operation (illustrated in Fig. 4) consists in roughly shaping the ends of the links externally by punching out the portions, a*, of the webs, a, between the links lying in the same plane or formed out of the same pair of webs. This operation is repeated on the other pair of webs, a’. Up to this point a continuous core of metal has been left at the intersection of the two pairs of webs.