Page:Popular Science Monthly Volume 46.djvu/624

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THE POPULAR SCIENCE MONTHLY.

bank-note business, as no one man can finish a note completely, but must find some one to help him.

The dies and bedpieces mentioned above are pieces of annealed steel—that is, steel that has been softened without decarbonizing—on which work has been engraved that is to be used several times on the same "job," or for a number of different plates. These dies, after "proving," are hardened by heating in cyanide of potassium, which is used in all hardening processes connected with the bank-note business. After these dies are hardened a roll made from very soft steel is rolled over the work under a pressure of from six to twenty tons to the line. This pressure is had by means of a machine called a transfer press.

PSM V46 D624 Transfer press.jpg

Fig. 6.—Transfer Press. A, Roll in carrier; B, die or bed piece; C, foot lever; D, rack to fasten lever down; E, side wheel by which bed of press is moved back and forth; F, rack and pinion connecting them; G, G, fulcrum pins of upper and lower levers; H, connecting rod between two levers; I, counter balance.

which, by a combination or compounding of levers, multiplies the pressure exerted by the operator from one hundred to one hundred and fifty times (Fig. 6).

By means of the large wheel on the side of the press, the shaft of which is geared into a rack fastened to the bed of the press, the roll, with this tremendous pressure still on it, is rolled back and forth on the die until the fine grain of the soft steel is forced into every line of the work. This gives the reverse of the die on