(3) Cutting out disks or blanks from the fillets.
If the weight of the blank is slightly below the standard weight, a somewhat larger cutter is used, so that the blanks may be of correct weight.
The blanks are charged into a hopper at one end of the furnace and conveyed towards the other end by a revolving Archimedean screw.
So my mind blanks stuff out?
He constantly leaves blanks for dates and facts, and many queries.
The spherical blanks soon gave place to lenticular-shaped ones.
(4) Adjusting the weight of the blanks (this is omitted in some mints).
(5) " Marking " or edge-rolling the blanks to produce a raised rim or to impress a design on the edge.
In the case of very large silver coins only one blank is cut in the width of the fillet, but bronze fillets are made wider so that three penny blanks are cut out at each stroke of the machine.
The cutting machines at the Mint work at 160 revolutions per minute, so that each of the eleven machines would be capable of cutting 19,200 blanks in an hour if it could be fed continuously.
The blanks are then passed to an edge rolling machine, by which they are thickened at the edge so as to form a rim to protect the finished coin from wear.
About 720 blanks are passed through this machine per minute.
In England gold and copper blanks are protected from oxidation, and after their passage through the furnace are merely washed in colanders with water and dried with sawdust in a rotating drum.
Silver blanks, however, are passed through rotary gas furnaces in which no attempt is made to exclude the air.
The blanks are converted into coin by receiving an impression from engraved dies.
The blanks are placed in the slide J and the lowest one is carried forward to the die in two successive movements of the " layer-on " K, a rod working backwards and forwards on a horizontal plate and actuating the finger L, fig.
In most foreign mints the blanks are weighed by the automatic balances before being struck, and those which are too heavy are reduced by filing or planing.
Heavy blanks have also been reduced chemically by making them part of the anode in a cyanide bath through which a current of electricity is passed.
Some metal from the surface of each blank then passes into solution, and the blanks are reduced in weight with remarkable uniformity.
A later series of shekels, belonging to the Roman period, are tetradrachms, "which came from the mints of Caesarea and Antioch and were used as blanks on which to impress Jewish types."
300, the practice of striking the blanks while they were hot was gradually discarded.
(6) Annealing the blanks and (in some mints) cleaning them in acid.
(7) Striking the blanks between dies surrounded by a collar.
When they have been reduced to the correct thickness they are examined by the " tryer," who cuts out one or two blanks from each fillet with a hand machine and weighs them on a delicate balance.
The cutters are so placed as to remove blanks in the manner shown in fig.
At the Royal Mint the blanks are passed between the parallel faces of a revolving steel plate and fixed block.
The blanks are next softened by annealing, and are then thoroughly cleaned before being passed to the coining presses.
The blanks fall through an aperture after having been heated for a few minutes.
The amount of copper removed from silver blanks containing 900 to 925 parts of silver per moo is from o 6 to I o per 1000.