The Rolling Room.
From the melting rooms through the corridor we reach the rolling room. The upright engine, on the right, of one hundred and sixty horse power, supplies the motive force to the rolling machines, four in number. Those on the left, are massive and substantial in their frame-work, with rollers of steel, polished by service in reducing the ingots to planchets for coining. The first process or rolling is termed breaking down; after that it requires to be passed through the machine until it is reduced to the required thinness—ten times if gold, eight if silver, being annealed in the intervals to prevent breaking. The rollers are adjustable and the space between them can be increased or diminished at pleasure, by the operator. About two hundred ingots are run through per hour on each pair of rollers.
The pressure applied is so intense that half a day’s rolling heats, not only the strips and rollers, but even the huge iron stanchions, weighing several tons, so hot that you can hardly hold your hand on them.
When the rolling is completed the strip is about six feet long, or six times as long as the ingot.
It is impossible to roll perfectly true. At times there will be a lump of hard gold, which will not be quite so much compressed as the rest. If the planchets were cut from this place, it would be heavier and more valuable than one cut from a thinner portion of the strip. It is, therefore, necessary to “draw” the strips, after being softened by annealing.
Rolling Machine.