Drawing is by the wet or dry process. The latter is used in drawing from No. 6 ( to No. 18, the lubricant employed being tallow and talc. The former is used for the higher numbers, the lubricant being a mixture of meal flour and water. By some wire-drawers the ef ficacy of stale beer is highly praised. After being drawn through several successivi Iv smaller dies the wire becomes hard and has to be annealed before the process an be continued. The annealing is followed by pickling, washing and beating to free it from scale. No. 6 wire can be drawn down to No. II in three passev, but from No. 14 down to No. 22 requires seven passes. To reduce the rod one-fifth of an inch in diameter to wire of one-twenty-fifth of an inch in diameter requires 12 drawings and three annealings. The speed at which the wire is drawn through the dies varies with its size and the kind of metal used — from 12 inches to 45 inches per second. Steel wire averages a speed of about 800 feet per minute; iron and brass, 1,000 feet per minute; and copper and silver about 1,200 feet per minute. For the very finest wire the dies arc of diamond or ruby.
In drawing wire the centre or core of the metal rod is pulled forward, the outer surface being held back by the friction of the die The ci•isequence is that a series of strains is set up in the wire which seriously affect its strertirh and this condition is removed by placing the coils in the annealing pots, where they are care fully scaled with sand to exclude the air, and are then exposed to a steady heat for a peri,..1 of eight or nine hours. Of the total finished product taken out of the annealing pots, a por tion is ready for the market without any further treatment; a portion is galvanized; hut a con siderable portion is converted into wire-cloth. wire nails and barbed wire. See IslAns.
Not all wire manufacture, however, is as simple a process as described above. In the mak ing of tungsten wire for electric lamps it is nec essary to develop a fibrous condition in the nat urally brittle metal. This is accomplished by rolling and hammering rods of the metal while it is red-hot. The operation of drawing also must be done with the hot metal. As tungsten is very hard the dies (of high-speed tool-steel) are quickly worn away. The heat and pressure at which the metal has to be drawn renders the ordinary oily or fatty lubricants of no avail and the only lubricant found effective is fine graph ite. This is smeared in paste form over the rod as it passes to the die, and just before it reaches that point a flame heats the rod and its graphite ointment to a red heat, burning in the graphite to a glossy black coating which so ad heres that the lubrication lasts for passes through several s essive dies. For the finest
sizes of tun the dies are diamonds.
Barbed ufactured in various pat terns. The rocess may be outlined by a brief descnpf of the machine employed in making what is known as 2-point Glidden barbed wire. Four coils of wire on reels are placed behind the machine. The wire from two of the reels serves to form the strands, while that from the other two is used to form the barbs. The two strand wires, which are larger than the other two, are led between a pair of friction wheels and pulled to a proper tension and then crossed by the other two transversely, one on each side. At fixed inter vals of a few inches, according to the desired spacing of the barbs, the two barb wires are caught by a pair of revolving fingers and twisted around one of the strand wires, and at the conclusion of the twist, two pairs of shears cut the ends of the barbs diagonally into sharp points. The wires then pass into a combined winding and twisting machine, by which the two strand wires are twisted around each other, and then to the spool where it is wound up ready for the market. When once started, the operation of wire making is continuous and rapid. The barbed wire used in trench warfare has from two to four times as many barbs as that for fencing cattle and requires additional reels and cutters in its production.
\\ ire in its several sizes is designated by number according to a scale or 'gauge,' de pending on its diameter. Several different gauges are in vogue in the United States and cause considerable confusion to the uninitiated. The Bureau of Standards at Washington rec ommends for ordinary steel wire the American Steel and Wire Company's gauge. For piano wire the bureau recommends the same com pany's 'Music Wire Gauge.' For copper wire and wire of all metals and alloys other than iron and steel the gauge in commercial use is the Brown and Sharpe wire gauge— also called the 'American \Vire Gauge.' The Birmingham wire gauge (B.W.G.) has been officially adopted by Conga's, and is in use by the United States Treasury Department in laying duties on impor tations. It is almost obsolete in economic prac tice. Consult Smith, 'Wire: Its Manufacture and Uses' t New York 1891); Allen, 1-1., 'Metal lurgical 51,innal of Iron and Steel' (London 1911); Charni•ck, G F.. 'Mechanical Tech nolog‘ ' (London 11)1c); Kind!. 'Rolling Milling Industry' (Cleveland, Ohio, 1913).