Rolling Machine.
Annealing Furnaces.
These are in the same room, to the right facing the rollers. The gold and strips are placed in copper canisters, and then placed in the furnaces and heated to a red heat; silver strips being laid loosely in the furnace. When they become soft and pliable, they are taken out and allowed to cool slowly.
The Drawing Benches.
These machines resemble long tables, with a bench on either side, at one end of which is an iron box secured to the table. In this are fastened two perpendicular steel cylinders, firmly supported in a bed, to prevent their bending or turning around, and presenting but a small portion of their circumference to the strip. These are exactly at the same distance apart that the thickness of the strip is required to be. One end of the strip is somewhat thinner than the rest, to allow it to pass easily between the cylinders. When through, this end is put between the jaws of a powerful pair of tongs, or pincers, fastened to a little carriage running on the table. The carriage to the further bench is up close to the cylinders, ready to receive a strip, which is inserted edgewise. When the end is between the pincers, the operator touches a foot pedal which closes the pincers firmly on the strip, and pressing another pedal, forces down a strong hook at the left end of the carriage, which catches in a link of the moving chain. This draws the carriage away from the cylinders, and the strip being connected with it has to follow. It is drawn between the cylinders, which operating on the thick part of the strip with greater power than upon the thin, reduces the whole to an equal thickness. When the strip is through, the strain on the tongs instantly ceases, which allows a spring to open them and drop the strip. At the same time another spring raises the hook and disengages the carriage from the chain. A cord fastened to the carriage runs back over the wheel near the head of the table, and then up to a couple of combination weights on the wall beyond, which draw the carriage back to the starting place, ready for another strip.
DRAWING BENCH.
The Cutting Machines.
After being thoroughly washed, the strips are consigned to the cutting machines. These are in the rear of the rolling mills, and are several in number, each when in active operation cutting two hundred and twenty-five planchets per minute. The press now used, consists of a vertical steel punch, which works in a round hole or matrix, cut in a solid steel plate. The action of the punch is obtained by an eccentric wheel. For instance, in an ordinary carriage wheel, the axis is in the centre, and the wheel revolves evenly around it. But if the axis is placed, say four inches from the centre, then it would revolve with a kind of hobble. From this peculiar motion its name is derived. Suppose the tire of the wheel is arranged, not to revolve with, but to slip easily around the wheel, and a rod is fastened to one side of the tire which prevents its turning. Now as the wheel revolves and brings the long side nearest the rod, it will push forward the rod, and when the long side of the wheel is away from the rod, it draws the rod with it.