PROCESS OF MANUFACTURE. Wire is almost universally manufactured by drawing, and the facility with which any metal can be drawn into wire depends upon its ductility. Alost metals have this property: but sonic, like antimony and bismuth, are so brittle that they can lie drawn out only with difficulty, and wire made from such metals is useless from want of tenacity. All metals largely used for making wire, such as steel, brass, and copper. are drawn by essen tially the same process. Steel billets first are rolled into round rods. The rods are cleaned of scale either by mechanical rubbing or more com monly by being immersed in an acid bath, and then dencidized by a bath of lime water. Each bar is then drawn into wire by pulling it through the holes of a draw plate. This is an oblong plate of hard steel pierced with conical holes, gradually diminishing in diameter and having the smaller ends of these tapering holes carefully prepared to the required size. Sometimes cubical shaped dies, each with a single trumpet-shaped hole, are used. The workman begins by making a point on the rod, so as to permit it to pass through the hole and be grasped by a pair of pincers attached to a chain. This chain is pulled along by suitable mechanism until the length of wire which has been drawn through the hole is sufficient to pass around a revolving drum. which
is then set in motion and draws the rod slowly through the draw plate, winding it upon itself as it revolves. From this drum the wire is passed through a smaller hole and wound on another drum, and so the process is repeated until the wire has been reduced to the proper size. Fine wire may require from 20 to 30 drawings. The drum revolves slowly with a thick wire and the speed is increased as the size diminishes. After being passed a few times through the draw plate the metal hecomes brittle and has to have its ductility restored by annealing. (See ANNEAL ING.) From the annealing furnace the wire passes to the acid bath to remove the scale and then to the lime water to remove the acid. It is then ready to be further reduced by the draw plate until annealing is again required. Gener ally a lubricant, wax, grease, soap. or other similar material, is employed during the drawing, especially for fine wires. For some very accurate purposes, such as chronometer springs and for gold and silver lace, the wire is drawn through holes perforated in rubies and other hard gems.