STAMPING OF METALS. There are different kinds of stamping. The plan adopted for producing coins or medals is described under MINT, and the preparation of the dies used, under DIE-SINKINO. For the ordinary stamped brass-work, so extensively made In Birmingham, a stamping-machine is employed, of which the essential parts are a die, a reverse or counter-die, and a hammer. A toothed rack, with arrangement for catching the hammer after it rebounds, is only used for special purposes, The die, which is made of east-iron or steel, is fixed to the bottom of the stamp. and the reverse is attached to the haunter, which works between two guides. Pieces of thin rolled brass are cut to size, and one placed upon the die; the hammer, with the counter-die, is now raised to a sufficient height by a windlass and rope, or other means, and allowed to tall, and thus force the thin plate into the die. The plates from the first blow are then annealed. Repeated blows and annealings follow until the article is "brought up," slight altera tions in the reverse being from time to time required. Sometimes as many as 30 blows are necessary, but 10 or 12 strokes will suffice for an object with a, considerable depth of raising. ,Globular articles are stamped in two or more pieces, and then soldered together.
The stamping process was first adapted to the production of hollow shapes in sheet iron by Mr. 'P. Griffiths in 1841; and since then, :he manufacture of such goods as dish covers, basins, and teapots ]bas been improved and extended to a surprising extent. In the case of a dish-cover, for example, a single sheet of iron is brought to the required shape by repeated stampings and buruishings upon a chuck. It is afterward tinned with-great ease, there being no joints to interfere with the operation; for the same reason, iron basins stamped out of a single sheet can be readily enameled. The old way of forming these articles by hand-labor was very tedious and clumsy.
German silver is too brittle a metal to be stamped like brass or iron, consequently it has only hitherto been made into small objects, such as spoons and forks, by this pro cess. But the Messrs. Elkington of Birmingham are now making articles of consider able size in this material, by means of a stamping-press worked by hydraulic power. A number of graduated dies are used for one object, each pair coming gradually nearer the desired shape, but none of them making au impression deep enough to strain the metal.
For stamping-machines used in dressing metallic ores, see METALLURGY.