The coining press used in all first-class mints is a wonderful exhibition of mechanical skill. Its frame is of cast-iron of several tons weight, with a central arch in which are placed the worlcing parts. The frame combines stability and rigidity. The mechanism of the working parts is automatic. The setting of the dies is a work of precision and can be properly done only by a person, who, being a skilled mechanic, has reinforced his native ability by long experi ence. In order to set his dies properly he must take into account the condition of the metal to be stamped, whether it be soft and ductile or hard and brittle. Upon these qualities of the metal depends the distance apart of the dies at the moment of their impact upon the planchets.
The blanks are fed into a vertical tube of equal diameter, and when the press is in motion auto matic fingers seize the bottom planchet by its periphery and carry it forward to a collar a little larger than the piece to be stamped. The piece drops into the collar, and a toggle joint causes the dies to approach each other and exert a pressure of about 160 tons upon the soft planchet. The planchet, being ductile, is by this pressure made to fill the entire space within the collar, which is grooved, and imparts the reeding to the edge of the coin. The finished coin is automatically released and falls into a pan below, to be followed by other coins at the rate of 90 or 120 per minute. The first number relates to large gold coins and silver dollars, the latter to small gold and small silver coins. It should perhaps be stated here that while the essential processes in coining are the same in all modern mints, the routine is not uniform. In the mint of the United States the coin after stamping is returned to the adjusting room and each piece weighed separately. The necessity for this arises out of the possibly defective rolling of the strip from which the blank is derived. The density of the metal varies some what, and there may be also defective sonority developed in the process of stamping. In order to secure sonorous coin it is sometimes the practice to ring every piece (this relates to gold coin and silver dollars), and if any fail to give the proper tone they are rejected and sent to the melting pot. The pieces which stand th, test are then returned to the coiner for conversion into uniform drafts for delivery to the superintendent or other officer authorized to receive and hold coined money of the gov ernment.
As a matter of law and regulation the coiner is required to make up gold coin into drafts of $5,000 of the uniform weight of 268.75 troy ounces. As the weight of the pieces separately weighed are not uniform, though all within the limit of legal tolerance, the coin is separated by the adjusters into "heavies," "lights" and "standard." Gold coins may vary from one fourth of a grain in the half and quarter eagles to one-half a grain in double eagles and eagles. The coiner takes "heavies," "lights" and in such proportions as will make drafts of 268.75 ounces and mingles them in the delivery pans. The drafts are then weighed, after counting the pieces in detail, and being found of the required weight, are set aside for final delivery. The drafts must not vary to exceed one one-hundredth of on ounce above or below the standard weight of $5,000, stated in the foregoing. Before delivery to the superintendent the latter takes a good number of pieces at random from the proposed delivery and care fully weighs them. If found within the legal limit of tolerance the delivery is accepted; but if the weight of any piece proves it outside of that limit the delivery is rejected, to be weighed, readjusted and recounted. It is proper to say that such a necessity seldom arises.
The practice now is to adjust all silver coins, excepting dimes. Dollars are made in drafts of $1,000 of the weight of 859.375 ounces. These drafts arc constituted of "heavies," "lights" and "standard," and the only variation from that standard weight is two one-hundredths of an ounce. Subsidiary silver coin is delivered in drafts of $1,000, of a weight of 803.75 ounces, with an allowance of two one-hundredths of an ounce for half and quarter dollars, which are adjusted, and one one-hundredth of an ounce for dimes, which are not adjusted. It will be seen that all of the processes involved in coining money are works of precision, from the break ing down of the ingot to the issue of the perfect coin. All must be rigidly calculated, nothing can be left to chance. The presence of any of the base metals, as well as of the rare and valuable ones, may destroy the ingot for coin age. Arsenic lead and antimony cause most of the unworkability of the money metals, but this disability is lessening through the process of advanced science.