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the crank-shaft, on which is also fixed a fly-wheel.Occasionally, in order that the fillet may he fed intothe press rapidly and with precision, a movable stop isadded, which takes its place in the last hole cut out,acting against the side nearest to the punch, and risingwith the upward stroke to permit of the forward motionof the fillet. At the English and Belgian mints, heavycrank presses are employed for cutting two or threeblanks at a time in bronze and sometimes silver.They are provided with a self-feeding arrangement,consisting of a pair of gripping rollers worked by aratchet motion. As in the case of bronze the filletsare not passed through the drawbench, and are there-fore thicker in the middle, it isfound advisable, when cuttingthree blanks from the width, tomake the central cutter somewhatsmaller than the external ones, inorder to secure greater uniformityin the weight of the coin. Thescissel is usually tied up in bundlesto be remelted.
Edge-Rolling or Marking .—In theRoyal Mint all blanks, after apreliminary examination to removesuch as are evidently imperfect, arepassed through the edge-roller orcompressor immediately on leav-ing the cutting-room, the objectof which is to raise a rim roundthe edge to facilitate the formationof the relief at the circumferencein the coining press, as also toprotect the impressed surfaces ofthe coin from undue wear. It isrepresented in the annexed engrav-ing, and consists of a circularsteel plate which rotates on ahorizontal axis, and having acircular groove on its face.
Opposite to the lower portion ofthis groove is fixed a steel block,on the face of which is a cor-responding groove, and the dis-tance between the two can boaccurately adjusted. The blanksare led to the space between thesetwo by means of an inclinedspout, at the upper end of whichrotates, in a vertical plane, a wheel provided on itsedge with slight saw-like indentations.
The metallic discs being led by means of a hopperto the top of this wheel, are distributed by its teeth,and pass down the guide with regular intervalsbetween them to the pair of confronting grooves, andthe distance between these being somewhat less thanthe diameter of the blank, its edge is pressed inwards,the thickness at the circumference being therebyincreased. In many continental mints an inscrip-tion or ornamentation is impressed on the edgeduring this operation. In England, however, it isleft perfectly smooth, the “milling” being producedin the subsequent operation of coining. It may be
mentioned, that this instrument is capable of “com-pressing ” blanks at the rate of about 700 per minute.
Annealing Blanks .—On leaving the edge-compressorthe blanks are subjected to the process of an-nealing, by which they are rendered sufficientlysoft to receive a well-defined impression of thedie in coining. The methods-adopted in the RoyalMint for annealing gold and silver coin haveduring the last few years undergone considerablemodification. Formerly gold blanks were treated inclosed iron tubes, and those of silver in open irontrays, but they are now all treated alike in coppertubes similar to those already described for anneal-
ing fillets. These tubes are nearly filled with theprecious metal, and above is placed a layer ofcharcoal, the whole being then covered with a copperlid: a number of them, containing in all about 3600ounces of gold, having been placed on an iron carriage,are pushed into the furnace, where they remain forabout twenty minutes. On their withdrawal thetubes are rapidly cooled by being plunged into water,by which means the oxidation which took placewhen they were allowed to cool slowly in the airis avoided. The blanks are now emptied into acopper colander, washed in cold water in order toremove the charcoal, and dried by agitation in asieve with hot sawdust over a heated iron table.
Fig. 29.
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