Punches Used In Fly-Presses, And Examples Of Their Products. Part 5
All the foregoing examples of punched works, suppose the punch to have been fixed to the follower of the press, and the matrix to the base of the same, in which case the bed punch requires to be very exactly adjusted by the set screws or dogs of the press. But it remains in concluding this section, to advert to a different arrangement in which the cutting tools are quite detached, and are far less liable to accident or fracture, even when the punches are of very large area and complicated figure, than when constructed in the ordinary manner with a shank by which they are united to the follower of the press. In this present case, the press has merely two flat surfaces six or eight inches in diameter, or square and of similar size, thereby more nearly resembling a hammer and anvil, of a very powerful and exact kind, to which the fly press was first compared.
* Patent granted to Mr. Julius Jefferys, for his improvements in curing or relieving disorders in the lungs. Sealed, 23rd January, 1836. Published in Repertory of Patent Inventions, Vol. vi., 4th Series, page 211. The patent respirator is very fully described, but not so the machinery.
Punches to be used in this manner, for works with various detached apertures requiring any especial arrangement, and for various straggling and complicated objects, are constructed as shown in figs. 963 to 965. There are two steel plates somewhat larger than the work, and from 3/6 to 3/8 thick, the plates are hinged together like the leaves of a book, but are placed sufficiently distant, to admit between them the work to be stamped out, and which is pinched between them by a thumb screw a. The two plates whilst folded together, are perforated with all the apertures required in the work, which perforations may be either detached, continuous, or arranged in any ornamental design that may be required. To all the apertures are fitted punches, which in length or vertical height, are about one eighth of an inch longer than the thickness of the upper plate, so as to stand up one eighth when resting on the material to be punched, as seen in the partial section 965, in which the work is shaded obliquely and the punch vertically.
As it would be difficult to fit the punches in one single piece to the ornamental or straggling parts of some devices, and as moreover such large and complicated punches, would be almost sure to become distorted in the hardening, or broken when in use, the difficulty is boldly met, by making the punch of as many small pieces as circumstances may render desirable, but which pieces, must collectively fill up all the interstices of the plate.
In using these punching tools, it is only necessary first to fix between the plates the metal to be pierced, then to insert all the punches into their respective apertures, and lastly to give the whole one blow between the flat disks of a powerful fly press, this drives all the punches through the work, and leaves them flush with the upper surface. The whole is then removed from the press, and placed over an aperture in the work bench, and with a small drift and hammer the punches are driven out of the plates into a drawer beneath, and on the plates being separated, the work will be found to be exactly perforated to the same design as that of he tool itself; or with any part of the design instead of the whole, if part only of the punches were inserted in their respective places, The punches are selected from amidst the corresponding pieces of brass, which latter are laid on one side, and the routine is recommenced.
It is by this ingenious application of punches that buhl works are stamped, as referred to in the foot note page 737 of this volume. If a honeysuckle should be the device, the piece of brass is first placed between the plate and punched out, and provided the punches are of the same length, the honeysuckle is removed in one piece although the punch may be in several; the wood is afterwards inserted, and is punched to exactly the same form, so that the brass honeysuckle will be found to fit in the most perfect manner as it is an exact counterpart of the removed wood.
The process is very economical and exact, but is only suited to large designs, because of the injury it would otherwise inflict on the wood, and on account of the expense of the tools, the mode is only proper for those patterns of which very large numbers are wanted; whereas the buhl saw is not liable to these limitations, but is of universal, although less rapid application.
Cut brads and nails or those which instead of being forged, are cut out of sheet iron by machinery, constitute the last example it is proposed to advance in this section.
Brads of the most simple kind as in fig. 966, have no heads, but are simply wedge form, and are cut out of strips of sheet iron, equal in width to the length of the brads, these strips are slit with circular shears, transversely from the ends of the sheets of iron so that the fibre of the iron may run lengthways through the nails.
When such brads are cut in the fly press, the bed has a rectangular mortise shown by the strong black line in fig. 966, the punch is made rather long and rectangular so as exactly to fill the bed, but the last portion of the punch, say for half an inch of its length, is nicked in, or filed back exactly to the size and angle of the brad, as shown in the inverted plan, in which the shaded portion shows the reduced part or tail of the punch. The punch is never raised entirely out of the bed, in order that the strip of metal may be put so far over the hole in the bed, as the tail of the punch will allow it, and also in contact with a stop or pin fixed to the bed, and in the descent of the punch its outer or rectangular edge removes the brad.
The strip of metal is turned over between every descent of the press, so as to cut the head of the one brad from the point of that previously made, and the double guides afforded by the tail and stop, enable this to be very quickly and truly done. The upper surface of the bed is not quite horizontal but a little inclined, so that the cutting may commence at the point of the brad, and thereby curl it less than if the tools met in absolute parallelism.
prev: Punches Used In Fly-Presses, And Examples Of Their Products. Part 4
next: Punches Used In Fly-Presses, And Examples Of Their Products. Part 6