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Encyclopedia Britannica - Main :: WIL-YAK |
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WIRE (A.S. wir, a wire; cf. Swed. vire, to twist, M.H.G. wiere, a gold ornament, Lat. viriae, armlets, ultimately from the root wi, to twist, bind) , a thin long rod of metal, generally round in section. The uses of wire are multifarious and diverse beyond all enumeration. It forms the raw material of important manufactures, such as the wire-net industry, wire-cloth making and wire-rope spinning, in which it occupies a place analogous to a textile fibre. Wire-cloth of all degrees of strength and fineness of mesh is used for sifting and screening machinery, for draining paper pulp, for window screens, and for many other purposes. Vast quantities of copper and iron wire are employed for telegraph and telephone wires and cables, and as conductors in electric lighting. It is in no less demand for fencing, and much is consumed in the construction of suspension bridges, and cages, &c. In the manufacture of stringed musical instruments and philosophical apparatus wire is again largely used. Among its other sources of consumption it is sufficient to mention pin and hair-pin making, the needle and fish-hook industries, nail, peg and rivet making, and carding machinery; indeed there are few industries into which it does not more or less enter. The physical properties requisite to make useful wire are possessed by only a limited number of metals and metallic alloys. The metals must in the first place be ductile; and, further, the wire when drawn
Diameter. Strain. In. lb. Gold . . . . 0162 5.61- 5.42 Platinum . .0161 6.70- 6.59 Silver . . .0157 7.86- 7.78 Copper . .0177 I0II-I0.2O Iron . . . . o169 II.I2-10.89 Copper . . . . .0605 233 Brass . . . . .0640 203 Steel . . o600 342 Phosphor Bronze .0630 394 Dr W. H. Wollaston first succeeded in drawing a platinum wire ~a-,5-6- inch in diameter by encasing a fine platinum wire within silver to ten times its diameter. The cored wire he then reduced to -auu inch, and by dissolving away the silver coating the platinum wire imv inch thick only remained. By continued treatment in this way wires of platinum for spider-lines of telescopes have been obtained of such extreme tenuity that a mile length of the wire 11 eighs not more than a grain; and it is said that platinum wire has been made which measures not more than 12 010 o mm., equal to less than the fifty-thousandth part of an inch. The accompanying table shows the comparative tenacity of the wire of metals and metallic alloys. Wire was originally made by beating the metal out into plates, which were then cut into continuous strips, and afterwards rounded by beating. The art of wire-drawing does not appear to have been known till the 14th century, and it was not introduced into England before the'second half of the 17th century. Wire is usually drawn
original
wire, and when it is pulled through the hole at the end its diameter becomes reduced accordingly. The action of drawing has the effect of hardening the wire and rendering it brittle, so that annealing must be done at intervals to soften it again for further drawing; the annealing is done in cast-iron pots, holding coils of wire which are raised to a red heat and then allowed to cool. Although the wire is kept air-tight as much as possible, some amount of scaling occurs, and pickling must be done to remove this scale before redrawing. An important point in wire-drawing is that of lubrication to facilitate the operation and to lessen the wear on the dies. Various lubricants, such as oil, tallow, soapy water and stale beer, are employed. Another method is to immerse the wire in a sulphate of copper solution, so that a film of copper is deposited which forms a kind of lubricant, easing the drawing considerably; in some classes of wire the copper is left after the final drawing to serve as a preventive of rust. The wire-drawing machines include means for holding the dies, accurately in position and for drawing the wire steadily through the holes. The usual design consists of a cast-iron bench or table having a bracket standing
block
block
Continuous wire-drawing machines differ from the single-block machines in having a series of dies through which the wire passes in a continuous manner. The difficulty of feeding between each die is solved by introducing a block between each, so that as the wire issues it coils around the block and is so helped on to the next die. The speeds of the blocks are increased successively, so that the elongation due to drawing is taken up and slip compensated for. The opera ion of threading the wire first through all the dies and around the blocks is termed " stringing-up." The arrangements for lubrication include a pump which floods the dies, and in many cases also the bottom portions of the blocks run in lubricant. The speeds at which the wire travels vary greatly, according to the material and the amount of reduction effected; rates from Too ft. up to 900 ft. are possible, the higher speeds being those of continuous machines.Wires and cables for electrical purposes are covered with various insulating materials, such as cotton
bitumen
steel taping. The stranding or covering machines employed in this work are designed to carry supplies of material and wind it on to the wire which is passing through at a rapid rate. Some of the smallest machines for cotton
Tapes of paper, rubber or jute are served from bobbins on disks and also in some designs from independent bobbins, each mounted on its own pin, set at a suitable angle in a frame, to give the spiral lead. In some instances seventy-two layers of paper are applied to high-tension cables. These cables are subsequently put into steam-heated tanks, hermetically sealed and connected to a vacuum pump, by which the moisture is drawn off as quickly as possible. When the cable is thoroughly dry a quantity of compound is admitted to the tank and so permeates the insulation. Lead is put on the outside of the paper in a press, which has dies through which the cable passes, and is covered with a uniform coating or tube of lead, forced into the dies and around the cable by hydraulic pressure. Steel tapes are in some cases used to armour cables and protect them from external injury; the tape is wound in a similar manner to the other materials already described. Rubber covering of wires and cables is done by passing them through grooved rollers simultaneously with rubber strips above and below, so that the rubber is crushed on to the wires, the latter emerging as a wide band. The separate wires are parted forcibly, each retaining its rubber sheathing. Vulcanizing is afterwards done in steam-heated drums. Many auxiliary
Wire Gauges.In commerce, the sizes of wire are estimated by gauges which consist of plates of circular or oblong form having notches of different widths round their edges to receive wire and sheet metals of different thicknesses. Each notch is stamped with a number, and the wire or sheet, which just fits a given notch, is stated to be of, say, No. 1o, Et, 12, &c., of the wire gauge. But it is always necessary to state what particular gauge is used, since, unfortunately, uniformity is wanting. Holtzapffel investigated the subject, and published a valuable collection of facts relating thereto in 1846. A more exhaustive report was published by a committee of the Society of Telegraph Engineers in 1879 (Journ. Soc. Tel. Eng. viii. p. 476), a result of which was the sanctioning by the Board of Trade, in 1884, of the New ImperiaLStandard Wire Gauge. That report stated: " The different gaug8 in use might he counted by hundreds. . . . Every wire-drawer has gauges adjusted to suit special objects. When competition is keen, wire is commonly drawn by one gauge and sold by another; half sizes and quarter sizes are in constant use among the dealers, the wire being sold as whole sizes. Sometimes four or five different gauge plates have been made by one makersome by which the workmen are paid, and others by which the wire is sold. . The whole system is in confusion, and lends itself to those who desire to use fraudulent practices." Thomas Hughes (The English Wire Gauge, London, 1879) stated that, " Inthe same town some use Stubs, some the Warrington, some the Lancashire, some the Yorkshire, some the Birmingham, some the iron wire gauge and some their own made wire gauge, all maintaining the gauge in their own possession to be the correct one." . Gauges may be broadly divided into two groups, the empirical and the geometrical. The first include all the old ones, notably the Birmingham (B.W.G.) and the Lancashire or Stubs. The origin of the B.W.G. is lost in obscurity. The numbers of wire were in common use earlier than 1735. It is believed that they originally were based on the series of drawn wires, No. t being the original
recent
The first attempt to adopt a geometrical system was made by Messrs Brown & Sharpe in 1855. They established a regular progression of thirty-nine steps between the English sizes, No. 0000 (46o mils) and No. 36 (5 mils). Each diameter was multiplied by 0.890522 to give the next lower size. This is now the American gauge, and is used to a considerable extent in the U.S.A. The Imperial Standard Wire Gauge, which has been sanctioned by the British Board of Trade, is one that was formulated by J. Latimer Clark. Incidentally, one of its recommendations is that it differs from pre-existing gauges scarcely more than they differ among themselves, and it is based on a rational system, the basis being the mil. No. 7/0, the largest size, is 0.50 in. (500 mils) in diameter, and the smallest, No. 50, is 0.001 in. (1 mil) in diameter. Between these the diameter, or thickness, diminishes by 10.557%, and the weight diminishes by 20%. But the fact remains that a large number of gauges are still in common use, and that gauges of the same name differ and are therefore not authoritative. Sheet iron wire gauge differs from Stubs' steel wire gauge. Gauges for wire and plate differ. Accuracy can only be secured by specifying precisely the name of the gauge intended, or, what is generally better, the dimensions in decimals, which can always be tested with a micrometer. A decimal gauge has been proposed. Tables of decimal equivalents of the wire gauges have been prepared, and are helpful. The circular forms of gauge are the most popular, and are generally 3; in. in diameter, with thirty-six notches; many have the decimal equivalents of the sizes stamped on the back. Oblong plates are similarly notched. Rolling mill gauges are also oblong in form. Many gauges are made with a wedge-like slot into which the wire is thrust; one edge being graduated, the point at which the movement
End of Article: WIRE (A.S. wir, a wire; cf. Swed. vire, to twist, M.H.G. wiere, a gold ornament, Lat. viriae, armlets, ultimately from the root wi, to twist, bind) If you wish, you can link directly to this article.
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