For the manufacture of iron wire the very best and toughest iron 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 ripping or rumpling, with the kind of machine described by Beckmann as probably the invention of LudoIf. 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 vice versa, 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 Wylie wire ; 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 braziers 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, it not usually submitted to 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 helea. 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 is 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 pritchcll. 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-iron. about two inches broad and one inch thick, covered on one side with a very hard composition called polin, which consists of fragments of east-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 tho forge. Being more fusible than the wrought-iroo, the potin is the first to melt : and sa soon as it begins to do so the plate is withdrawn from the fire and gently hammered; and the heating 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 ; and while the bar remains hot the boles 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 holes 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 is 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. Mouchel, at in the department of l'Orne, is 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 begins 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 plates 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 reserved for steel wire.