The threads of the one piece
produce indentations in those of the other, but they are not so
deep as when produced by the former method.
122. Embossing upon leather. This art of copying from
patterns previously engraved on steel rollers is in most respects
similar to the preceding. The leather is forced into the
cavities, and the parts which are not opposite to any cavity are
powerfully condensed between the rollers.
123. Swaging. This is an art of copying practised by the
smith. In order to fashion his iron and steel into the various
forms demanded by his customers, he has small blocks of steel
into which are sunk cavities of different shapes; these are
called swages, and are generally in pairs. Thus if he wants a
round bolt, terminating in a cylindrical head of larger diameter,
and having one or more projecting rims, he uses a corresponding
swaging tool; and having heated the end of his iron rod, and
thickened it by striking the end in the direction of the axis
(which is technically called upsetting), he places its head upon
one part of the lage; and whilst an assistant holds the other
part on the top of the hot iron, he strikes it several times with
his hammer, occasionally turning the head one quarter round.
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