Buttons embossed with crests or
other devices are produced by the same means; and some of those
which are plain receive their hemispherical form from the dies in
which they are struck. The heads of several kinds of nails which
are portions of spheres, or polyhedrons, are also formed by these
means.
132. Of a process for copying, called in France clichee. This
curious method of copying by stamping is applied to medals, and
in some cases to forming stereotype plates. There exists a range
of temperature previous to the melting point of several of the
alloys of lead, tin, and antimony, in which the compound is
neither solid, nor yet fluid. In this kind of pasty state it is
placed in a box under a die, which descends upon it with
considerable force. The blow drives the metal into the finest
lines of the die, and the coldness of the latter immediately
solidifies the whole mass. A quantity of the half-melted metal is
scattered in all directions by the blow, and is retained by the
sides of the box in which the process is carried on. The work
thus produced is admirable for its sharpness, but has not the
finished form of a piece just leaving the coining-press: the
sides are ragged, and it must be trimmed, and its thickness
equalized in the lathe.
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