98S 



WIRE-DRAWING. 



WIRE-DRAWING. 



is selected. Before the process of rolling with grooved rollers had 

 become common, this superior iron was prepared for the drawing- 

 machine by extending it with the hammer into convenient rods, about 

 the thickness of the little finger. These rods were further reduced in 

 thickness and extended in length by a coarse kind of drawing, called 

 rifpiny or rumpling, with the kind of machine described by Beckmann 

 as probably the invention of Ludolf. Holland, writing about 1833, 

 states that although this contrivance is now rarely to be seen in the 

 large wire-mills of this country, it remains in use in some old esta- 

 blishments ; and also that in France, and among the continental manu- 

 facturers generally, iron wire was, until within a late period, altogether 

 drawn by such an apparatus. 



In modern practice both iron and steel, but especially the former, 

 are prepared for the final drawing by passing between grooved rollers, 

 made with the greatest accuracy. The rollers used for this purpose 

 are generally at least seven or eight inches in diameter, and are some- 

 times made to perform 350 revolutions in a minute. A bar of steel 

 thirty inches long and an inch square, heated to redness, is passed 

 between the rollers, through grooves successively diminishing in size, 

 eight times in less than a minute, and is thereby elongated to from 

 twenty to thirty feet. As it would be difficult and inconvenient to 

 pass the rod back between each rolling, in order that it might always 

 enter the grooves in the same direction, three rollers are used, placed 

 one above the other, so that when the wire has passed in one direction 

 between the two upper rollers, it may pass back in the opposite 

 direction between the two lower rollers, and rice vend, thus avoiding 

 any loss of time, heat, or labour in passing it backwards and forwards. 

 For ordinary wire the rods are commonly reduced to a thickness of 

 about one-eighth of an inch by this process. The slender rods thus 

 produced are called, from their appearance, black wire, to distinguish 

 them from drawn or 6> iyht mre ; and, on account of its cheapness, 

 such wire is preferred for coarse purposes in which it is either to be 

 painted or concealed from view. It is commonly used by tinmen and 

 i>M/Krs for strengthening the rims of pots, kettles, and various kinds 

 of tin-ware and copper-ware. The kind of cast steel wire of which the 

 best needles and some other articles are made, i^ not usually submitted 

 t<j the rolling process, but, after being tilted to about a quarter of an 

 inch square, it is rounded on an anvil previous to elongation by the 

 draw-plate. 



In whatever way the metal may have been prepared for the ultimate 

 process of drawing, or whatever may be the motive power employed in 

 that process, it is essentially the same. The draw-plate is usually 

 formed of a stout piece of shear-steel, about six inches long and an 

 inch and a half in diameter, flattened on one side. It is pierced trans- 

 versely with several conical holes, the larger orifices of which open 

 upon the flattened surface of the plate, while their smaller orifices are 

 carefully finished to the size to which it U intended to reduce the wire 

 drawn through them. When the holes have become enlarged by use, 

 their smaller orifices are reduced by hammering, and then reopened to 

 the proper size and form by means of a long taper needle called a 

 '/ The art of making draw-plates has been carried to much 

 greater perfection in France than in this country ; and in time of war 

 French draw-plates have been sold for their weight in silver. The 

 French plates consist of a bar of wrought-iroo. about two inches broad 

 and one inch thick, covered on one side with a very hard composition 

 called potin, which consists of fragments of cast-iron pots, broken with 

 the hammer, and mixed with pieces of white-wood charcoal. One 

 side of the wrought-iron bar is hammered to a furrowed surface, and 

 covered to the depth of about half an inch with pieces of the pre- 

 pared potin ; the whole is then wrapped up in a coarse cloth, which 

 has been previously dipped in clay and water mixed to the consistency 

 of cream, and finally put in the forge. Being more fusible than the 

 wrought-iron, the potin is the first to melt : and as soon as it begins to 

 do so the plate is withdrawn from the fire and gently hammered ; and 

 the beating and hammering are repeated alternately until the union of 

 the two metals is complete. The plate is subsequently reheated, and 

 extended by hammering to double its original length ; the harder 

 metal being so perfectly united with the other as to form a malleable 

 alloy with it ; and bile the bar remains hot the holes are formed by 

 punching. For this operation the bar is four times heated, and after 

 each reheating a finer punch is employed, so as to make the boles 

 taper. The holes are formed from the wrought iron side of the bar, 

 and are not carried completely through by the plate-maker ; the com- 

 pletion of the holes being performed with sharp punches when the 

 plate a cold, by the wire-drawer himself. Another mode of producing 

 draw-plates, practised at one of the principal wire-manufactories in 

 France, that of the Messrs. Mouchul, at 1'Aigle, in the department of 

 1'Urne, in by arranging several pieces of wrought-iron in the form of a 

 box without a lid, and filling the cavity with cast-steel. The whole is 

 then covered with a luting of clay, heated until the steel begin* to 

 melt, and worked with a hammer in a similar way to that above 

 described. When draw-plates have been hammered up several times, 

 to reduce holes worn too large by use, they become so hard as to 

 require annealing. After every precaution has been observed, draw- 

 plate* will vary somewhat in hardness; but those which are too soft 

 for drawing iron wire may be used for brass, while the very hardest 

 are rrwrved for steel wire. 



The modes of determining the thickness of wire, and the improve- 



ments in graduation suggested by Holtzapffel and Whitworth for this 

 purpose, are noticed under GAGE. 



In drawing wire by hand the draw-plate is laid against two upright 

 pillars fixed on a bench or table, and, the extreme end of the wire 

 to be drawn being so reduced as to enable it readily to pass through 

 the hole, a small portion is drawn through by a lever apparatus. 

 When a sufficient length of wire has thus been brought through 

 the plate, it is secured to a conical or cylindrical drum, which is 

 mounted upon a vertical axis opposite to the hole in the draw-plate. 

 The workman then takes in one hand the coil of thick wire to be reduced, 

 and in the other a lever handle attached to the drum; and while 

 he turns the drum so as to wind the wire upon its circumference, 

 and consequently to draw it through the plate, he imparts a kind of 

 twist to the wive which enters the plate, by a peculiar motion of 

 the hand in which the coil is supported. In drawing coarse wire, 

 which requires considerable power, the workman walks round the 

 bench at each revolution of the drum, carrying the lever round 

 with him ; but for finer wire the apparatus is much lighter, aud 

 requires very little labour. In factories where inanimate power is 

 used the winding-cylinders are turned by bevil-gearing underneath 

 the bench, and the coil of undrawn wire is placed on a reel. This 

 apparatus is accompanied by an ingenious contrivance which allows 

 the drum to fall out of connection with the gearing, and consequently 

 to cease to revolve, as soon as the piece of wire is drawn completely 

 through the plate. In some eases, as for pinion wire, which would be 

 injured by winding upon a drum, wire is drawn upon a long draw- 

 bench in a straight line, the power, which is equalised by the use of 

 a fly-wheel, being applied to a winch-handle which, by means of spur- 

 gear, imparts motion to a horizontal rack. 



Between the repeated drawings which are requisite to reduce wire, 

 especially of the finer or smaller sizes, to the required degree of 

 tenuity, it is necessary frequently to heat and anneal it, by which 

 processes the fibrous character imparted by the drawing is in some 

 degree removed before a fresh extension takes place. The annealing- 

 oven should be so contrived as to avoid oxidation as much as possible, 

 and to heat all sizes of wire with tolerable uniformity, the thickest 

 being placed in such a situation as to receive most heat ; and afti-r 

 leaving it the wire must be scoured or washed to free it from whatever 

 oxide may have formed upon its surface. In order more perfectly to 

 remove the oxide (which, if left on the surface, not only impairs the 

 appearance and the strength of the wire, ' but also injures the draw- 

 plate) the coil of wire is sometimes immersed in starch-water or stale 

 beer-grounds during the operation of drawing. A curious and im- 

 portant discovery was made some years since at an eminent wire- 

 manufuctory, where, in order to heat the acid liquor in which the 

 annealed wire was steeped, some ingots of brass which happened to 

 be at hand were made red-hot and quenched in it. It was sub- 

 sequently found that, owing to the action of the acid upon the bras?, 

 the iron wire had become coated with a thin film of copper, which 

 greatly facilitated its passage through the draw-plate, acting, it would 

 appear, like a lubricating medium. So important was the advantage 

 gained, that the practice has been universally adopted in that factory 

 of iming a weak solution of copper in the acid liquor in which iron 

 or steel wire is washed. The film of copper is entirely removed by 

 the last annealing process. The operation of drawing is also facilitated 

 by the free use of grease, or, for the finer descriptions of wire, wax, 

 to lubricate the wire as it passes through the plate. The repeated 

 annealings of steel-wire would deprive it of too much of its carbou, 

 but for the practice, which is not pursued with iron wire, of surround- 

 ing it with charcoal-dust while in the furnace. The rapidity of the 

 drawing process must vary with the quality of the metal, the hardest 

 steel wire requiring the slowest motion ; but as each successive draw- 

 ing increases the fibrous or filamentous character of the metal, the 

 rapidity of the extension may be safely increased as the wire becomes 

 more and more attenuated. 



Even when made with the greatest possible care, the holes of iron 1 1 

 steel draw-plates will enlarge so much with wear as to render it impos- 

 sible lo draw any very great length of wire perfectly uniform in thick- 

 ness. To remedy this, Mr. Brockcdon obtained a patent in 1819 for 

 making draw-plates, the holes of which consist of diamonds or other 

 hard precious stones. Dr. lire states that with a plate of this kind 

 mounted with a ruby, pierced with a hole 'U033 of an iiu-h in diameter, 

 a silver wire 170 miles long has been drawn so perfectly uniform, that 

 no difference could be detected either by weighing portions of equal 

 length or by measuring with a micrometer. 



Dr. Wollaston communicated to the Hoyal Society, in the year 1813, 

 a method of drawing wire of extreme tenuity, suitable tor use in 

 micrometers. This be accomplished, in the first instance, by boring or 

 drilling a rod of silver, longitudinally, with a hole one-tenth of its own 

 diameter, aud then filling it with gold. The compound bar being 

 drawn into wire 3i,th or jfcth of an inch in diameter, the silver was 

 afterwards dissolved in heated nitric acid, leaving a perfect gold wire 

 i.isit' 1 or s<>th f an mc b m diameter. Finding the operation of 

 drilling the silver rod very troublesome, he subsequently drew platina 

 wire, and cast the silver round it, treating the compound bar as before. 

 Even by ordinary processes, brass wire is made so thin, that gauze may 

 be woven from it hich will have 67,OuO meshea in a squ ire inch. The 

 extreme ductili ty of the precious metals is still more strikingly illustrated 



