Walter Breen
Prior to 1835, the hubbing process was limited to imparting the central-device (heads and wreaths). The Mint had tried in 1798 to hub a complete large cent reverse. This complete hub was used to produce the last 15 reverse dies used in 1798, the reverse of 1799 number 3, all of the 1800 reverses, and reverse A and G of 1801. (See Half Cent Encyclopedia, pp. 21-22.)
This experiment met with less than satisfactory results-each die had to be reworked by hand to strengthen parts of the design that did not properly impress. Further attempts at hubbing complete dies were abandoned until introduction of the new processes in 1835. (The Mint made one more abortive attempt to hub full dies in 1834 on the Capped Bust half dollars, Overton varieties 113 and 114, apparently using information sent back from Europe by Franklin Peale. See Ivan Leaman, "1834 0113 & 114 Capped Bust Halves: A Different View", John Reich Journal, October 1992.)
Breen speculated that this was due to the screw presses not being powerful enough to impart the design," However, this is clearly not the case as the Mint records show that the presses used for hubbing were the same ones purchased in 1794 and 1795. (Stewart, p. 175, warrants of March 25 and June 3; pp. 178-179, warrants of February 2 and May 11; p. 184, warrant of December 31; these are the heaviest presses purchased by the Mint. Several smaller presses were subsequently purchased, but these were likely used as cutting presses. The last press through the 1850s was purchased in 1827; "Ledgers and Blotters of Ordinary Receipts and Expenditures", Dec. 11, 1827, Record Group 104, entry 181. Presses may have been purchased after this, but this would be well after the hubbing of full dies began.)
Furthermore, both Waldo Abbott's 1861 account of his visit to the Philadelphia Mint and Mint records (including the annual report by the Director of the Mint) show that screw presses were used to hub dies at least until the arrival of hydraulic presses in 1893, and possibly after that. (Waldo Abbott, "Making Money", Harper's Monthly Magazine, Nov.-Dec. 1861; see also, Annual Report of the Director of the Mint, 1896 and 1902.)
To hub a full die, the die blank was machined, placed in a screw press, and given one or two blows, as previously explained. At this point, the die was removed, annealed, and the excess metal pushed up by the hubbing was machined away to form a frustum, or truncated cone. If this disturbed metal was not machined away, and a frustum not formed, metal flow and, therefore, further hubbing of the die, was restrained. If any part of the design was not "coming up," hand engraving was done to help the metal flow. The die was then cleaned and the process repeated until the design was complete. (Denis Cooper, The Art and Craft of Coin Making, 1988, p. 162-164. See also the previously referenced pages of the Peale Report.)
The problems with the experimental hubbed dies, and the fact that the Mint suddenly became capable of hubbing full dies after Peale's return from Europe, show that the real problem was the Mint's own inexperience. As previously mentioned, all of the hubbed reverse dies show considerable hand reworking of the peripheral lettering and small details-this is exactly what would be expected if the Mint did not understand the need to machine away the disturbed metal and handwork the die between blows.
Once the die was completed, it would be prepared for hardening. In the early days, hardening was the "moment of truth." Many dies cracked or shattered during hardening and others broke apart immediately upon use. These problems have been previously attributed to poor die steel. While the Mint did use this excuse on at least one occasion (Taxay, U.S. Mint and Coinage, 1966, p.121.) this was nothing more than official scape goating. The real problem, again, was the Mint's inexperience with the demands of coining, especially that of die forging. (For a full discussion, see Sholley, "Inexperience, Not Die Steel, Caused Problems at Early Ll.S, Mint", Penny-Wise, March 1996.)
Upon his employment in 1795, Eckfeldt introduced a new hardening process, which many numismatists believe he developed. This is based on an article by "Mr. K" (presumably then Chief Engraver William Kneass) which appeared in The Franklin Journal. (Vol. I, No.2, February 1826, pp. 97-99.)
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On Hardening Steel Dies at the First United States Mint
Mr. Editor, I avail myself of the opportunity you offer, to record in your useful repository, the observations made by ingenious practical mechanics, in the prosecution of their respective arts. It will no doubt comport with your views to give merit to its just due, by stating the processes already known, as well as to make the knowledge of them more extensive.
The management of steel for nice purposes in the arts, is of vast importance, and requires considerable practical skill; it has consequently been made the subject of numerous experiments, which within the course of a few years have resulted in the discovery of many improvements. The general method of hardening this metal is to heat it red hot, and then plunge it into cold water, and sometimes into mercury, in order to reduce its temperature as quickly as possible; to effect this cooling with the requisite rapidity, the article when plunged, is moved about, in order to expose it to new surfaces of the cold fluid. This method answers in general, with small or thin pieces of steel, but not when the mass is considerable; in this case, the article frequently breaks in the operation, or is hardened at the edges only; from this cause much inconvenience, and great loss, have frequently resulted to those interested in the hardening of steel dies, for striking medals, coins, &c. This has been frequently experienced in the Mint of the United States; the dies after being completely finished, excepting the process of hardening, were very often destroyed in this attempt; or if they passed sagely through this ordeal, were found to be incapable of sustaining the severe and repeated blows to which they, in their use, were subjected. An intimate friend of the writer, it is believed, was the first person who succeeded in obviating these difficulties so completely, that not the slightest danger is now apprehended from the process.
Mr. Adam Eckfeldt, the present chief coiner in the Mint, a very ingenious practical mechanic, whose original profession was that of a smith, was employed in the infant state of the establishment, to manage this department. Aware that the cause of the frequent failures in the process alluded to, was the sudden contraction of the steel on the outside, whilst the inside was in a heated and expanded state, causing the outer hardened and brittle coat of steel to crack or burst, he adopted the following expedient. He caused a vessel holding 200 gallons of water, to be placed in the upper part of the building, at the height of 40 feet above the room in which the dies were hardened; from this vessel, the water was conducted down through a pipe of one inch and one quarter in diameter, with. a cock at the bottom, and nozzles of different sizes, to regulate the diameter of the jet of water. Under one of these was placed the heated die, the water being directed on the centre of the upper surface. The experiment was first tried in the year 1795, and the same mode has been ever since pursued, without a single instance of failure.
By this process the die is hardened in such a way, as to best sustain the pressure to which it is to be subjected, and the middle of the face, which by the former process was apt to remain soft, now becomes the hardest part. The hardened part of the die so managed, were it to be separated, would be found to be in the form of a segment of a sphere, resting in the lower soft part as in a dish; the hardness of course gradually decreasing as you descend towards the foot. Dies thus hardened, preserve their forms until they are fairly worn out.
I am aware that the above mode is now in frequent use, as Mr. Eckfeldt never wished to keep it secret; a gentleman of the Mint, communicated the process to a friend in Birmingham, England, where, it is believed, it was not previously known.
Should you think the above information worth publishing, you will probably receive some other communications, containing improvements effected by the same gentleman.
Yours very respectfully, K.
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