THE ductility of many of the metals and alloys, or the quality which allows them to be drawn into wire, is applied to a variety of curious uses in the manufacturing arts, and the process may be viewed as the sequel to the use of grooved and figured rollers; but the ductile metals submit to this process with various degrees of perfection

In drawing wire, the metal is first prepared to the cylindrical form, either directly by casting, or between rollers with semicircular grooves; and the process is completed by pulling the metal through a series of holes gradually less and less, made in a metallic plate, by which the wire becomes gradually reduced in size, and elongated; but as in rolling, the process of annealing must be resorted to at proper intervals.

In general, the draw-plates are made of hardened steel, and they arc formed upon the same principle, whether for round, square, or complex sections, either solid as wires, or hollow as tubes; the substance of the metal is partly kept back, as in a wave, by a narrow ridge within the draw-plate, acting as a burnisher.

The section of the holes is explained by fig. 60, p. 178, which represents one of the jewel draw-plates patented by Mr. Brockedon, for gold, silver, and other fine wires; but the plates are generally made of hardened steel, or else of alloys of partly similar nature, which allow the holes to be contracted and repaired, by closing them with blows of a pointed hammer or punch around the hole.

The holes for round wires are sometimes ground out from both sides upon the same brass cone or grinder, the sides of which vary in obliquity from 10 to 30 degrees, according to the metal to be drawn; for the sake of strength the ridge is mostly nearer to the side on which the metal enters, and the sharp edge is also removed, either by wriggling the plate upon the grinder in order to round the inside, or in any other manner.*

The end of the wire is pointed to enable it to be passed through the hole, and it is then caught by a pair of nippers, themselves at the extremity either of a chain, rope, toothed rack, or screw, by which the wire is drawn through by rectilinear motion. The nippers or dogs resemble very strong carpenters' pincers or pliers, the handles of which diverge at an angle; they are sometimes closed by a sliding ring at the end of the strap or chain, which slides down the handles of the nippers; there are some other modifications, all acting upon the same principle, of compressing the nippers the more forcibly upon the wire the greater the draught. It requires a proportionally strong support to resist the strain; and to avoid the fracture of the hardened steel draw-plate, it is usually placed against a strong perforated plate of wrought-iron. In manufactories where large quantities of wire are made, the wire is more usually attached to the circumference of a reel, which is made to revolve by steam or other power.

It is necessary often to anneal the wire, but no general rule can be stated in respect to its recurrence; and before resuming the drawing process, the wire is invariably immersed in some acid liquor or pickle, to remove the slight coating of oxide, which would otherwise rapidly destroy the plates, (as many of these metallic oxides are used in polishing,) in general some lubricating matter is applied to reduce the friction, as beer-grounds, starch-water or oil; and for gold and silver, wax is generally used. (See note A B, Appendix, Vol. II. page 974.)

Most of the wire is drawn upon reels, and is therefore met with in circular coils, and it is necessary, in almost every case, to straighten it before use. The soft or annealed wires, such as the copper wire used for bell-hanging, the soft iron binding-wire used in soldering, and others, are stretched and straightened by fixing the one end, and pulling the other with a pair of pliers; or short pieces of soft wire may be straightened by rolling them between two flat boards.†

* Sometimes the plate is made with three cones instead of two; the third cone is exaggerated in fig. 302, p. 429, which represents the arrangement for drawing tubes, the central cone being just equal to the wave, or the quantity the metal is reduced. Under any circumstances all the keen edges are removed, as they would tear instead of compress the material.

† Soft steel wire for making needles is straightened by rolling or rubbing: it is

The hard-drawn and unannealed wires, used for making pins, bird-cages, blinds, and numerous other wire-works, are too elastic to yield to the above methods, and fig. 291 represents the mode employed to take the spring out of them, or in other words, to straighten these hard wires. The coil of wire on the reel f which revolves on a pin, is drawn through the riddle g, by the pliers. The riddle is a piece of wood or metal with sloping pins, which lean alternately opposite ways, so as to keep the wire close down on the board, and yet to compel it to pursue a slightly zigzag, or rather serpentine course, which is considerably magnified in the figure.*

The pins are equivalent to the three forces a, b, c, of the bending machine, page 3S9, several times referred to. Were the three first pins critically placed, they would suffice to bend the wire to the limit of its permanently elastic force, and would leave it perfectly straight; commonly however, five pins are used, and sometimes seven or nine. The same riddle will not serve for wires differing in diameter; and were this simple tool more expensive so as to render it desirable, a universal riddle might be made cut up in lengths of 4 or 5 inches, and arranged in cylindrical bundles, within iron hoops of 4 inches diameter; the rubber is a bar of cast-iron about two feet long, narrow enough to lie between the rings. See Lardnors Cyclopedia, Vol. 2, by placing the pins b and d, under a simple screw-adjustment; but in actual practice, a tap of the hammer is found sufficient to correct their positions.