WIRE-DRAWING
WIRE was not always made by drawing. In early days metal-workers were wont to beat out their metal into thin plates or leaves, to cut the plates into narrow strips, and to round these strips by a hammer and a file until they assumed the form of wire. In the description of the sacerdotal garments prepared for Aaron, it is stated that the makers of the ephod, “did beat the gold into thin plates, and cut it into wires, to work it in the blue, and in the purple, and in the scarlet, and in the fine linen, with cunning work.” In the regions of fable, Vulcan is declared to have forged a net of delicate wirework to entrap Venus and Mars; and if that most respectable of blacksmiths forged his wire we may presume that he did not draw it. It is supposed that wire-drawing first commenced at Nurnberg about five centuries ago; the wire-smiths then changing their designation to wire-drawers. The delicate gold-work of Nurnberg was probably the first to which the improvement was applied; but copper and brass, iron and steel, afterwards shared the advantage; and the French and English wire-smiths became also in due time wire-drawers.
The making of wire is not only a simple but an instructive process; for it shows that cold iron is more like dough that we are in the habit of supposing. It can be squeezed and driven about, until that which was a thick rod becomes a thin wire; as a bulky lump of dough can be squeezed out into a long roll. The iron is rolled hot into rods before it reaches the wire-drawer. He provides himself with hard steel plates, pierced with holes varying from the size of the original rod, down to that of the smallest wire. One end of a rod is tapered, pulled through a hole, and grasped by nippers on the other side; and then steam or any other power draws the whole rod forcibly through; necessarily reducing the thickness, and at the same time increasing the length. Then it is dragged through the next smaller hole, and through the next, and through the next, until it has attained the required degree of dainty tenuity; the same wire my decrease from one-third to one-fiftieth of an inch in thickness, but it requires many gradations in reduction, and many intermediate annealings to prevent it from becoming too brittle. It is not merely iron that is so treated; any metal possessing a moderate degree of ductility can be attenuated by drawing as well as by hammering or melting, varied in degree, and in the manner in which the process is conducted. Steel, we know, is made into wire for needles and fish-hooks, and a vast number of other articles; brass is made into wire for pins, among a countless host of other applications; copper is made into wire for electrical telegraphs, bell hanging and scientific apparatus; gold and silver are made into wire for ornaments; platinum is made into wire for philosophers and chemists.
A rare list of names and numbers is met with in relation to iron wire. There is in the first place, Iron Wire, plainly so called, varying in numerical designation according to its thickness, and sold in bundles weighing sixty-three pounds each. There is, in the second place, Best Best Iron Wire – a tautology which may be excused so long as we talk about Baden Baden; this has numbers similar to the former, and it is sold in bundles of the same weight, but is slightly higher in price. There is, in the next place, Best Selected Charcoal Wire, a little advanced again in price: and there is Card Annealed and Bright Iron Wire, of larger diameter, and much higher price; but we need not enter into these trade secrets. Let us be content to know that wires of various metals, and greatly varied sizes, find their way into the hands of artificers innumerable, who fashion them into needles, bodkins, pins, hooks and eyes, fish-hooks, button rings, hair pins, card-teeth, wire-brushes, brush-wires, spiral springs, bonnet stiffeners, and a great number of articles that we can here afford to enumerate.
As unity is strength, so do many wires bring their strength to bear upon one object when they are twisted; and thus will a rope of twenty wires often render braver service than twenty ropes separately. This twisting of wires around each other is a work not differing much in principle from the making of hempen cables, hawsers, ropes, cords, lines, and twines; each wire is a component element of the group; and it is only because the metal wire is stiffer than the hempen yarn, that any more elaborate manufacturing machinery becomes necessary.
The useful purposes to which wire rope, and cord, and string, are now applied are surprisingly numerous. Window-sash lines, hothouse cords, lightening conductors, picture frame cord, clock cord, tent ropes, clothes lines – all are gradually traveling from the hempen region to the wire region. The wire-workers stoutly assert that their favourite material is cheaper, more durable, little less flexible, and much less bulky than hempen cords. And, instead of a single wire for fences, railway signal cord, and the like, much stronger line is produced by a strand or twisted cord of smaller wires. The makers tell us that a wire rope one inch in circumference, and weighing one pound per fathom, will bear as great a strain, and render as much useful service as a hempen rope two inches and three-quarters in circumference, and weighing two pounds per fathom: this being the ratio maintained up to greater sizes: a four inch wire-rope having as much strength as a ten-inch hempen rope. Is it not wonderful that a wire rope of four inches circumference, or only an inch and a quarter in thickness, will bear a weight of thirty tons, more than sixty thousand pounds, before it will break? On one occasion the artillery officers at Woolwich spliced an eight-inch hempen cable to a wire rope three inches and a half in circumference; they pulled and stretched, and pulled and stretched again, until one of the two broke, - it was the hempen cable that gave way, leaving the wire rope as sound as at first.
Landsmen know little of the difference between standing-rigging and running-rigging on shipboards; but it may be easily understood as referring – on the one hand, to ropes which are fixed in definite positions in a ship, and on the other to ropes which have to be hauled in, and hauled out, hauled up, and hauled down, during the daily working of a ship. Now, wire ropes are coming extensively into use for standing rigging, their strength presenting a favourable contrast to that of hempen ropes. The General Screw Company’s ships Propontis, Bosphorus, and Hellespont, have wire-rope standing-rigging; and it is said that the Hellespont, on one of her voyages, put the wire rope to a severe test; for, during a shattering and clattering of booms and sheet-cleets, the iron wire shrouds broke a boom, instead of the boom breaking the shrouds.
Wire is getting into public buildings, in positions and situations where one would scarcely look for it. For instance, an ingenious firm set themselves to consider whether wire might not fulfill the duty of lath and plaster for ceilings; and the Chester County Lunatic Asylum affords an answer in the affirmative. There are wires placed about a quarter of an inch apart, and connected by cross wires, at intervals of about eight inches, and this arrangement affords a holding-place for the plaster, with which the ceiling is afterwards coated. As wire bends so easily, it is considered that such a construction is likely to be highly useful in domes and arched ceilings. And as wire gets among the plasterers, so does it find a reception among the cotton-spinners; for the cotton is carded, as a preparatory step towards spinning, by means of cylinders studded all over with fine wire teeth, springing out of strips of leather and arranged in scrupulous order by a beautiful machine, which does the work of a forest of fingers at once.
The grandest achievement, perhaps, of the world’s wire-workers, is the formation of a bridge, or rather the support of a bridge made of other materials. This is really a great and important work. Engineers say that iron wire is stronger, weight for weight, than bar-iron; that cables are more easily lifted into their places that bar-chains. At least some engineers say this, and they have given proof of their belief in the construction of very remarkable bridges. Travellers in Switzerland speak in wonderment of the wire-bridge at Freyburg; in which the span from pier to pier is nearly nine hundred feet; in which the platform is nearly a hundred and seventy feet above the water; which platform is supported by four cables, each consisting of more than a thousand iron wires. They speak, too, of another wire bridge across the gorge of Gotterou. But these bridges have been outdone by others which have recently been thrown across the mighty Niagara, owing to the extraordinary nature of the falls, and rapids, and boiling eddies ruling beneath. With a span of eight hundred feet from shore to shore, and a height of two hundred and sixty feet above the water, a light and elegant bridge presents its delicate tracery of wire-work against the sky, near the great North American Falls, in an extraordinary manner.
There are sixteen wire cables to support the bridge; there are six hundred wires in each cable; and these wire cables less than an inch in thickness, support a foot-bridge which weighs altogether more than six hundred tons. The bridge is about a mile and a half below the widely-renowned Falls, and directly over the frightful rapids. It was finished about six years ago; but there has since been constructed another Niagara wire bridge, to be traversed by the locomotive, and intended to connect the railway system of the United States with that of Canada. In this remarkable bridge, the trains, instead of running through a tube, as in our Britannia Bridge, run along top of a tube; the tube being supported by four wire cables, two above and two below; and as these enormous cables are nearly three thousand four hundred wires each, we may perchance be prepared to expect that the weight of iron-wire employed exceeds half a million pounds. A wire bridge over the Ohio, at Wheeling, though not comprising so many wires in the cables, is longer than those at Niagara; it is indeed not trifling achievement to support a bridge a thousand feet long by wire; there are twelve cables of four inches diameter, each containing five hundred and fifty wires. If the good people of Quebec ever have the fortune to witness the completion of the proposed railway bridge over the mighty St. Lawrence, they will see a wire bridge that will throw all others into the shade. A bridge three thousand four hundred feet long, with piers three hundred feet high, and sixteen hundred feet apart; a roadway wide enough for both horse-vehicles and for a railway, at a height of a hundred and sixty feet above the water, and all supported by wire ropes – will be a monument of skill, enterprise, and utility, which – with the grand trunk railway itself – will help the Canadians to a better character of perseverance and activity than they have hitherto enjoyed.
It is a brave affair to make an electrotelegraphic cable. We are accustomed to such things now; but two or three years ago they were wonders to be marveled at. When Messrs. Newall produced the wire-work, and the Gutta Percha Company produced the gutta percha work, for the Anglo-French submarine telegraph in the summer of eighteen hundred and fifty-one, the achievement was worthily recorded as an honour to our age. Many of those who now read this sheet will remember that the cable was twenty-four miles long; that it consisted essentially of four copper wires insulated in a bed of gutta percha; the strand or cord thus formed was bound round tightly with spun yarn; and around this strand, as a central core; were twisted ten galvanized iron wires. A huge mass it was; for when all completed, it formed a coil of thirty feet in diameter on the outside, fifteen on the inside, five feet high, and weighing a hundred and eighty tons. A great work was the manufacture of this cable. In the first place, at the Gutta Percha Company’s works, about a hundred miles of copper wire, in fair equal lengths, were coated and coated again with this singular gum; and then they were transferred to a cable-making factory at Wapping. The four coated wires were groupel, and were bound round with hempen yarn steeped in a solution of tar and tallow, by the aid of a machine. This rope, if it may be so called, was passed vertically up a tube, around which were ten large bobbins filled with galvanized wire; and while the rope was traveling upward, and the bobbins were busily rotating on their axes, the wire, unwinding from the bobbins, coiled itself in a hard twist around the rope, compassing the hemp and the gutta percha closely, without allowing the all-important copper telegraphic wires in the centre to come in contact one with another.
And so again, in eighteen hundred and fifty-three, when the still more remarkable “line of thought” was prepared to stretch from England to Belgium. The Calais cable is encircled by ten twisted wires, but the Belgian cable is encircled by twelve; the length of the former is twenty-four miles, but of the latter the length is upwards of seventy miles; of the former the weight is a hundred and eighty tons, but of the latter not much less than five hundred tons. For aught that is yet known, the wire-drawers and wire-twisters could do their part towards the construction of a submarine telegraph across the very Atlantic itself, if the difficulties in other directions can be surmounted. The internal copper for these and other telegraphs are sometimes coated with gutta percha in a similar way. The engineers who, about six years ago, laid down four or five hundred miles of telegraph from Berlin to Frankfort-on-the-Main, thus coated their wire; they had a box or small chamber with eight small holes on one side, and eight larger holes on the opposite; they put eight copper wires in at the small holes and out again at the larger; they forced in hot gutta percha by a piston, and forced out the eight wires, each with a close wrapper of gutta percha.
He who would know all the forms into which wire is now twisted, and woven, and linked, must rise betimes and give me a long day to it. He must look at the wire-netting fences, for excluding hares and rabbits from gardens, for enclosing poultry-yards and pheasantries, and for guarding tender young plants. He must see how this wire is galvanized for some purposes, to render it durable without painting or tarring. He must know something about very strong wire-netting for confining sheep and dogs; and the various kinds used for aviaries, trellis-work, flower-training, window-guards, and sky-lights; and wire fencing of a more ornate character for gardens and pleasure grounds; and wire-pheasantries, something like large bird cages; and pheasant or hen coops; and wire garden-borders, around flower-beds and parterres; and wire plant-guards, encircling the young plants and shielding them from all intruders; and stronger tree guards made to open at the sides. There are, too, wire fences, with or without wire netting attached; wire umbrellas or canopies, around and over which roses may cluster in the middle of a flower-bed; wire flower-stands, for conservatory, or greenhouse, or hall; wire chairs and garden seats, wire gauze blinds, wire bird cages; wire fire guards and fenders; wire lamps and lanterns; wire meat covers and meat safes; wire lattice for bookcases and windows; wire sieves and strainers; wire cloth for flax-dressing and paper-making. The wire-gauze is a pretty material, woven in a loom as if it were some fibrous material. We have seen some brass wire-gauze so exquisitely fine as to have sixty-seven thousand meshes in a square inch.
Our readers are not unfamiliar with the sad narratives of coal-pit explosions, Davy lamps, and fire-damp. Yet we may spare a dozen lines or so, to explain how it is that iron wire plays so important a part in the clever bur neglected contrivances for lessening such disasters. In the great coalfields of our northern counties, the seams of coal give forth large quantities of carbureted hydrogen, called by the miners fire-damp. This fire-damp mingles readily with common air, and a certain ratio between the two produces an explosive compound; and when a light approaches such a compound, an explosion ensues which produces the devastation so often recorded in the newspapers. Even while we now write, public attention is directed to a dread calamity whereby nearly a hundred human creatures in one pit have been destroyed by an explosion of fire-damp. It was to guard against these awful scenes that Sir Humphrey Davy invented his beautiful safety lamp. If a fine gauze be woven of iron wire, the iron cools a flame too much to allow it to pass through the gauze. Davy, therefore, said: - “if a miner’s lamp be surrounded by iron-wire gauze, and the fire-damp passes through and becomes kindled, the flame cannot come out again, but becomes cooled and extinguished, and air-ignited gas passes out instead, thereby preventing the fire-damp in the rest of the mine from becoming ignited.” He was right. In Dr. Clanny’s improvement on Davy’s lamp, the wire gauze has about thirteen hundred meshes in the square inch. The principle is sound and beautiful; but the practice is sadly overlaid with negligence and blunder.
The manufacture of gold-lace affords a pretty exemplification of the making and using of wire. Gold-lace, however, is not gold-lace, for the gold is but a covering for silver-lace; and indeed silver-lace is not silver-lace, for the silver is but a covering for silk-lace. A knotty enigma this, altogether. Gold-lace may be considered as a kind of ribbon, of which the coarse and weft threads are of silk coated with gilt silver. How the metal becomes gradually thinned and thinned, until fitted to perform its work, is curious to see. First, a good stout rod of solid silver is prepared, perhaps an inch in thickness by a couple of feet in length. The rod is heated; a layer of leaf-gold is placed upon it; this layer is burnished down; another layer is placed and burnished; and another, and another, and another – several layers of gold, but a trifle after all; for to a pound of silver there may perhaps be not more than a hundred grains of the more precious metal. Then is the gilt-silver rod annealed, and drawn successively through many holes in a steel plate, until reduced to a slender rod about one-fifth of an inch in diameter: the gold, like the silver, becoming elongated as it becomes thinned. Then the wire-drawer takes it, and draws and draws and draws until the slender rod becomes a minute wire – using holes pierced through rubies when the wire becomes very fine indeed. And then the wire is flattened, and is wound or spun upon a silken thread, and the threads so made are woven or braided into a ribbon. But of what thickness is the silver wire with which the silk is encased? It seldom exceeds the size of a delicate hair And of what thickness is the gold with which the silver is encased? Arithmeticians and manufacturers have laid their heads together, and have come to a conclusion, that the gold on the finest gilt-silver wire does not exceed in thickness one-third of a millionth part of an inch; and yet it is uniform and homogeneous, without breaks even when viewed under the power of a moderate microscope. A little slate-and-pencil work will show that, if a coined sovereign could be beaten or drawn out to this almost inconceivable degree of thinness, it would form a ribbon an inch in with, and long enough to engirdle the Crystal Palace at Sydenham, wings, and towers, and all!
Filagree is another pretty kind of wire-work. Silver wire, or gold wire, or gilt silver wire, is here twisted into fantastic and artistic forms, partly by the fingers and partly by small tools and machines. Some of the productions in this art, especially those produced in Italy and in India, are wonderful for the patience bestowed upon them. It is scarcely English art: we seem to be busy and bustling to bestow time on these prettinesses. The wire is very thin, but of course much exceeding the thickness of the film of gold on the silver wire for gold lace. Perhaps the thinnest bit of wire ever actually made and isolated was that produced by Dr. Wollaston, a philosopher who had an extraordinary knack of doing things which no one else could do. He procured a small rod of silver; he bored a little hold through it from end to end; he inserted into this hole the smallest platinum wire he could procure; he subjected the silver rod to wire-drawing processes, until it became the finest of silver-wires with a platinum filament running along its centre; he dissolved the silver in warm nitrous acid – and there remained and exquisite little platinum wire, one thirty-thousandth of an inch in thickness!