In the manufacture of steel pens, (see page 942-3,) it is important to have an exact control over the punches which cut the slits, and those which mark the inscriptions, as by descending too far they might disfigure the steel, or even cut it through. Accordingly Mr. Mordan introduced between the head of the press and the lever, an adjustable ring which acts as a stop, and only allows the punches to descend to one definite distance; until in fact the ring is pinched between the press and lever.
The screw of the fly-press, is sometimes superseded by a con-trivance known both as the toggle-joint, and as the knee-joint. The two parts a, b, and b, c, fig. 953, are jointed to each other at b, the extremity c, is jointed to the upper part of the press, and c, to the top of the follower. When the parts a, b, and b, c, are inclined at a small angle the extremities a, and c, are brought closer together, and raise the follower, but when the two levers are straightened, a and c separate with a minute degree of motion, but almost irresistible power, especially towards the completion of the stroke. The bending and straightening of the toggle-joint, is effected by the revolution of a small crank, united to the point b, fig. 953, by a connecting rod b,f.
* See Encyclopedia Metropolitans, part Manufacturers, article Coining.
Presses with the toggle-joint are perfectly suited to cutting out works with punches and bolsters, provided the relative thickness of the work and tools are such, as to bring to bear the strongest point of the mechanical action, at the moment the greatest resistance occurs in the work; but as the fly-press with a screw is in all cases powerful alike, irrespective of such proportions, provided alone that there is sufficient movement to create the required momentum, the fly-press is more generally useful.
The cut 954 refers to a lever press worked by an excentric, and used in cutting brads and nails, which will be again alluded to when this manufacture is briefly noticed.
It is now intended to describe a few examples of works executed in fly-presses, giving the preference to those appertaining to mechanism.
The round disks of metal for coin are always cut out with the fly-press, and are then called blanks, the punch being a solid cylinder, the bed or bolster a hollow cylinder that exactly fits it. In the gold currency, more especially, great care is taken to make these punches as nearly as it is possible mathematically alike in diameter, and the sheets of gold also mathematically alike in thickness, by aid of the drawing rollers or rather drawing cylinders referred to in vol. i., page 428; but notwithstanding every precaution the pieces or blanks when thus prepared do not always weigh strictly alike. This minute difference is most ingeniously remedied, by using the one error as a compensation for the other. Trial is made at each end of every strip of gold, and by cutting the thicker gold with the smaller punches, the adjustment is effected with the needful degree of accuracy, so that every piece is made critically true in weight, without the tedious necessity for weighing and scraping, otherwise needful.
Buttons are made in enormous quantities by means of the fly-press. That metal buttons should be thus cut out with tools and stamped with dies, will be immediately obvious to all, but the fly-press has been also more or less employed in making buttons of horn, shell, wood, papier-mache and some other materials. Amongst others may be noticed the silk buttons called, Florentine hut tons, each of which consists of several pieces that are cut out in presses, then enveloped by the silk covering, and clasped together at the hack, (in the press,) by a performed iron disk, the margin of which is formed into 6 or 8 points that clutch and hold the silk, whilst the cloth by which the button is sewed on, is at the same time protruded through the center hole in the back plate of the silk button; details that may be easily inspected by pulling one of them to pieces. Indeed great ingenuity has been displayed, and many patents have been granted, for making this necessary article of dress, a button.
Round washers that arc placed under holts and nuts in machinery, are punched out just like the blanks for coin; although in punching the larger washers, that measure 5 and
6 inches in diameter and 1/4 inch thick, with the ordinary flypresses, the iron requires to be made red hot.
The round or square holes in the washers are made at a second process with other tools, and to ensure the centrality of the holes, some kind of stop is temporarily affixed to the lower tool. The more complete stop is a thin plate of iron hollowed out at an angle of from 90 to 120 degrees and screwed on the top of the bed, as this may be set forward to suit various diameters. But the more usual plan, is to drill two holes in the bed, to drive in two wires, and to bend their ends flat down towards the central hole as also shown in fig. 955 overleaf, the ends of the wires are filed away until, after a few trials, it is found the blank when held in contact with the stops by the left hand, is truly pierced; the whole quantity may be then proceeded with as rapidly as the hands can be used, with confidence in the centrality of all the holes thus produced.
Chains with flat links that are used in machinery are made in the fly-press. The links are cut out of the form shown at a, fig. 956, the holes are afterwards punched just as in washers and one at a time, every blank being so held that its circular extremity touches the stops on the bed or die, and thereby the two holes become equidistant in all the links, which are afterwards strung together by inserting wire rivets through the holes.
The pins or rivets for the links, are cut off from the length of wire in the fly-press, by a pair of cutters like wide chisels with square edges, assisted by a stop to keep the pins of one length; or by one straight cutter and an angular cutter hollowed to about