Illustrated history of the United States mint / with a complete description of American coinage, from the earliest period to the present time

by Unknown

MILLING MACHINE.

The planchets, after being adjusted, are received here, and, in order to protect the surface of the coin, are passed through the milling-machine. The planchets are fed to this machine through an upright tube, and, as they descend from the lower aperture, they are caught upon the edge of a revolving wheel and carried about a quarter of a revolution, during which the edge is compressed and forced up—the space between the wheel and the rim being a little less than the diameter of the planchet. This apparatus moves so nimbly that five hundred and sixty half-dimes can be milled in a minute; but, for large pieces, the average is about one hundred and twenty. In this room are the milling machines, and the massive, but delicate, coining presses, ten in number. Each of these is capable of coining from eighty to one hundred pieces a minute. Only the largest are used in making coins of large denominations.

PERFECTED COINING PRESS.

COINING PRESS.

The arch is a solid piece of cast iron, weighing several tons, and unites with its beauty great strength. The table is also of iron, brightly polished and very heavy. In the interior of the arch is a nearly round plate of brass, called a triangle. It is fastened to a lever above by two steel bands, termed stirrups, one of which can be seen to the right of the arch. The stout arm above it, looking so dark in the picture, is also connected with the triangle by a ball-and-socket joint, and it is this arm which forces down the triangle. The arm is connected with the end of the lever above by a joint somewhat like that of the knee. One end of the lever can be seen reaching behind the arch to a crank near the large fly-wheel. When the triangle is raised, the arm and near end of the lever extends outward. When the crank lifts the further end of the lever it draws in the knee and forces down the arm until it is perfectly straight. By that time the crank has revolved and is lowering the lever, which forces out the knee again and raises the arm. As the triangle is fastened to the arm it has to follow all its movements.

Under the triangle, buried in the lower part of the arch, is a steel cup, or, technically, a “die stake.” Into this is fastened the reverse die. The die stake is arranged to rise one-eighth of an inch; when down it rests firmly on the solid foundation of the arch. Over the die stake is a steel collar or plate, in which is a hole large enough to allow a planchet to drop upon the die. In the triangle above, the obverse die is fastened, which moves with the triangle; when the knee is straightened the die fits into the collar and presses down upon the reverse die.

Just in front of the triangle will be seen an upright tube made of brass, and of the size to hold the planchets to be coined. These are placed in this tube. As they reach the bottom they are seized singly by a pair of steel feeders, in motion as similar to that of the finger and thumb as is possible in machinery, and carried over the collar and deposited between the dies, and, while the fingers are expanding and returning for another planchet, the dies close on the one within the collar, and by a rotary motion are made to impress it silently but powerfully. The fingers, as they again close upon a planchet at the mouth of the tube, also seize the coin, and, while conveying a second planchet on to the die, carry the coin off, dropping it into a box provided for that purpose, and the operation is continued ad infinitum. These presses are attended by ladies, and do their work in a perfect manner. The engine that drives the machinery is of one hundred and sixty horse-power.

After being stamped the coins are taken to the Coiner’s room, and placed on a long table—the double eagles in piles of ten each. It will be remembered that, in the Adjusting Room, a difference of one-half a grain was made in the weight of some of the double eagles. The light and heavy ones are kept separate in coining, and when delivered to the treasurer, they are mixed together in such proportions as to give him full weight in every delivery. By law the deviation from the standard weight, in delivering to him, must not exceed three pennyweights in one thousand double eagles. The gold coins—as small as quarter eagles being counted and weighed to verify the count—are put up in bags of $5,000 each. The three-dollar pieces are put up in bags of $3,000, and one-dollar pieces in $1,000 bags. The silver pieces, and sometimes small gold, are counted on a very ingenious contrivance called a “counting-board.”