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.
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