Wire has been used in Europe for more than 400 years. At first it was made by drawing do\yn, in blacksmith fashion, with the hammer upon the anvil. The draw-plate was in vented in Germany about 300 years ago, but it was comparatively little used until recent times. Now, tlie rolling-mill and the draw-bench arc combined into one system of manufacture, by means of which the rate and diminished cost of production have developed the trade so enormously as to have led to the use of iron and steel wire for ropes, bridges, fencing, telegraph, and so many other new purposes, that it 1ms at length become a great branch of industry. Hollow tubes are now manufactured oi' all sizes, and out of all the ductile metals. This apparently difficult process is accomplished in several ways. With one system it is done by first forming a hole through a short, dumpy piece of metal, either by casting or drilling; into this hole a mandril is inserted, and then the dumpy mass, by means of the drawing process or by rolls, is passed through a succession of holes until it covers the mandril from end to end. This mandril may be fine wire, or large enough to form the tubes for a steam boiler. A similar process, but substituting rolls for the draw-plate, is mostly employed for the larger sizes. The same or similar principle is frequently employed to make tubes, close at one end, these tubes being of various sizes; in such case the holes are not passed entirely through the mass; the mandril is inserted and is then pushed through the successive holes in the draw-plate, until the metal is extended over the mandril. Sometimes the piece is formed from a disk into a thimble-form, and then put on a mandril to be elongated, 'There is also an extensive manufacture of iron wire and of iron tubes, both being covered with a thin brass tube, by which means not only beauty but greater strength is obtained at a reduced rate; and for such purposes as these articles are used, viz., picture-rods, hand-rails, shop windows, carpet rods, and such like, the arrangement fulfills the object equal -to an entire brass structure. The iron wire or tube is made as before described ; the outer brass tube is made in a similar manner, but sufficiently large to admit of its being slipped over the iron. The iron may now be considered as a mandril, and the two are drawn through the draw-plate together, thu3 fixing the thin brass tube upon the iron, while the whole surface exposed is brass. The so-called copper wire which is now extensively used by upholsterers for the spring cushions of sofas, beds, and similar purposes, is merely iron wire, which is made in the ordinary manner until just before the last process, when it is immersed in a solution of sulphate of copper for a short time, sufficient to allow a thin film of copper to be deposited on the surface of the iron wire. The iron wire thus covered with copper is now drawn through a draw-plate, by which it is rendered hard and clastic and suitable for a spring, at the same time the dull surface of the deposited copper is made as bright as a new farthing, and serves to protect the wire from oxidation. There is yet another application of the natural law, which a few years ago would have been reckoned an impossibility —it is the process for drawing conical tubes. Nothing yet said will explain how this can be done. A taper mandril will suggest itself, which, so far. is simple. But the die of varying diameter, how is that to be obtained? For a long time rolls for rolling taper gun-barrels have been in use, in which a succession of tapering grooves are formed, while, by dexterous management, the roller contrives to insert the thick end of the gun barrel at the precise point in the revolving rolls, and thu3 the gun-barrel is elongated towards the muzzle by means of the narrowing groove in the rolls; bayonet blades arc likewise drawn out in the same manner. In the process to which I now refer, for the drawing out of the long tapering brass tabes, an expanding die is used for a draw-plate. This die consists of a ring of block-tin containing [1 small percentage of copper, to give it a little greater rigidity; this ring is applied at the smaller end of the mandril, and the brass is dawn through the die. By this means two effects are produced, first, the metal is drawn over the mandril to a small extent, and secondly, the die is destroyed, from the extension to which it has been subjected; it is therefore thrown into the melting-pot, to be cast into a new die, and thus by a succession of new dies, the metal is gradually drawn over the steel taper mandril, until it is covered with brass from end to end, when the steel mandril is withdrawn. There is yet another remarkable process in connection with this natural property, which is taken advantage of in the formation of ornamental twisted tubes of various patterns, such as we sec in tho gas iittings of churches and other places. To producc snch tubes, tho brass is first drawn into a plain tuba upon a mandril, in the way described; this plain tube is then passed through a succession of revolving blunt screw-tools, having the required form upon their interior surface. In form the tool is arranged as a screw-nut, but not being adapted to cut tho metal, and the plain tube being without a mandril, its surface is slightly depressed by the screw pressure, and by a suqcession of such screw-tools, or nuts, it is finally depressed to the finished ornamental pat tern as required. We sometimes see these ornamental tubes of a diamond screw pattern, where the spiral is crossed by another spiral, uniformly along the entire surface. This is done by means of two sets of screw tools, one set turns to the right hand, the other set to the left hand, and between the two the pattern is formed. This pattern may be of any section, plain, .square, octagonal, ribbed, rounded, or otherwise, all depend ing on two principles; first, the flowing properties of the atoms of the'imetal, and secondly, the copying arrangement by which the required pattern is transferred to the tube under operation, thus shifting the relative position of the molecules, yet without cutting the metal. Referring again to the wire-drawing process, such is the effect produced by the operation that, contrary to what might have been expected, the strength of the wire or steel is greatly increased. In the case of iron of an ultimate strength of 25 tuns per inch, it is increased in strength fully 10 tuns, and some of the best iron, with a strength of 28 tuns, is raised to 40 tuns. The most remarkable change in this respect is in the case of steel music-wire. The mild steel out of which this is mltde has a strength, when in the natural state, of from 30 to 40 tuns, according to its steeliness, but when tempered mildly, by being made red-hot and then cooled in oil, and elongated into wire, its strength is increased fully three-fold. At the same time, if such steel or even iron wire is made red-hot, so as to allow the natural law to assert itself, all these high conditions vanish, with only one redeeming quality, that the wire then becomes more pMaMe and similar in strength to the iron or steel out of which it was made. The knowledge that this treatment of steel has the effect of increasing its strength and toughness so enormously, has produced fruits in several directions. One of these, bearing on the present subject, is the attempt to draw steel tubes of any tegt^ or section or substance. Throughout the engineering world there are many purposes (indeed wherever motion is involved) for which a strong light material would be extensively applied, provided it could be obtained at a moderate cost. To accomplish this operation, a hole or slit, according to the section required, is first formed in a short thick mass of steel; two dies are employed, the one internally (which remains in use throughout the operation), the other externally (which has to be exchanged for a smaller one at every passage). Then enormous hydraulic pressure is brought to be!1r in pulling it through the vacant space between the internal and the external dies, thus leaving a portion of the steel behind, which forms a reservoir of steel for the in- ci"eased. length, by future elongating with that which could n°t pass through at the rate of motion of the apparatus, but to follow suit as it has opportunity, and then, by annealing the mass of steel, and using smaller and smaller external dies in succession, the thick lump becomes gradually elongated into any length of any section, and, if necessary, with the high qualities of the music wire. WU.li t'ne object of carrying ont such a manufacture, a c°mpany was recently formed in London, to produce steel tubular forms of any size or section. A variety of remarkable sp'Ocimens was produced by them which made every engineer's mouth water, and although commercially it has not succeeded (simply because the arrangements of the world were not quite ripe for it), still that, judging by all past experience, does not affect the question any more than the receding wave affects the rising tide. The grand fact remains that it is a possibility, by sufficient pressure and patience, to cause solid steel to flow into any hollow form of section without breaking its continuity ; it is a wonderful triumph of mind over matter which cannot be ignored, and which has yet to accomplish most important results in the future history the mechanism of the working world of applied mechanics, and the advantages are so apparent and so numerous that its ultimate success is only a question of time. My chief object in making the foregoing remarks, is chiefly to show that the natural laws which govern materials and things, are a great lesson to be taught to our young students, before they enter the workships of applied mechanics, and to show that tho varied operations of the practical worker are thus intimately blended with the profoundest philosophy, and that the fashioning of matter into the various forms required by our civilization, is not the drudgery to a thinking mind which it is generally considered to be, but that we are fellow-workers in carrying out and taking advantage of the natural laws, as laid down for men by the Grand Designer of the Universe.
This article was originally published with the title "Wire and Tube Drawing" in Scientific American 21, 23, 354 (December 1869)