Roughing Mill.—The roughing mill consists usually of eight pairs of rolls, in which the billet is reduced from a 4-inch x 4-inch section to a three-fourths inch square section, and it is in this mill that the steel receives the first in stalment of that thorough mechanical working which contributes so greatly to its ultimate tensile strength. Each pair of rolls is placed at an increasing distance from the one that pre cedes it, in order to allow for the increase in length due to the decrease of section of the billet. It has been found, moreover, that by changink the shapes of the grooves in the sue-, cessive pairs of rolls, making them alternately square and oval, oval and round, etc., there is not only an economy of power secured, but a more thorough working or manipulation of the metal is obtained, and its qualities are propor tionately improved. In the eighth set of rolls, or ((pass,) as it is technically known, the grooves are three-quarters of an inch square. From these, the last pair of roughing rolls, the rods are carried to the finishing mill.
Finishing Mill.— In this mill the wire rods are given commonly 10 more passes and brought down to the required dimensions. The finishing mill generally lies at right angles to the rough ing mill; and instead of the rods passing through pair after pair of rolls in a continuous straight line, they pass through the successive rolls in alternating directions, describing half circles between each pair. In order to guide the rods into the proper rolls, workmen stand be tween each pair, and as the rod issues from the rolls it is seized with a pair of tongs, bent around through a half-circle and fed to the next "pass.D Consequently, when a rod mill is in full blast, it presents one of the most in teresting sights. Owing to the rapid decrease in section and increase in length, as the rod passes through the successive rolls, it is neces sary that the speed of the successive rolls be increased; and by the time the rod issues from the tenth roll of the finishing mill, it is travel ing at a speed of 1,350 feet per minute, or about 15 miles an hour. As the whole of the rolling down from the 4-inch x 4-inch billet to the finished rod, which will be, say, 13-64 of an inch in diameter, is done at one heat, it can be understood that the scene is extremely pictur esque. In order to protect the men who stand between the pairs of rolls and direct the course of the rods, a series of curved semi-circular guards or shields are fastened upon the iron floor of the mill. The amount of working to which the steel is subjected, and the great horse power that is required to perform this duty, may be judged from the fact that the billet, which at the first pass through the mills was 4 inches x 4 inches in section and only 3 feet long, as it issues from the last pair of rolls is a scant quarter of an inch in diameter and measures no less than 1.189 feet, or not far
from a quarter of a mile in length. As the rods leave the last pair of rolls the ends are caught up and attached to the drums of a set of reels, on which they are wound up into a convenient coil for further handling. As soon as the coil is completed, it is dropped from the reel onto the floor of a conveyor, by which it is carried to the wire mill.
Wire-Drawing.— Up to this point the product is known by the technical name of and it is only after it has been drawn down in the dies that it is known commercially as ((wire? Wire-drawing has the advantage of permitting the production of a much smaller wire than could be produced under the rolls, while the very process of drawing down the wire greatly enhances its physical qualities, in creasing the tensile strength to a truly remark able degree. The wire-drawing machine con sists of a stout bench, on which is mounted a strong cast-iron drum, on which the wire is wound as it is drawn through the plate. The draw-plates, or die-plates, as they are called, are stout blocks of cast steel which are per forated with conical holes, carefully gauged to the exact desired size of the wire. The holes have a slight taper, the wire, of course, enter ing at the larger end of the hole. The coil of wire is placed on a spool located on the floor of the shop near the bench, and the end of the wire having been swagged down is passed through the die-plate and attached to the drum, which then proceeds to wind up the wire until the whole coil has been drawn down. As the wire-drawing is done cold, it can be well under stood that with several score of these machines running at the same time it requires very powerful motive power to drive the mill. An increasing quantity of wire is now drawn to special shapes other than round — some square, or flat, some of D-section, or with a groove, these being adapted to various mechanical uses. After it has been drawn down, it is necessary to remove the strains in the wire, and it is ac cordingly taken to the annealing room, where it is loaded into large annealing pots. After the pot is filled, it is carefully sealed with sand to exclude the air, and the wire is exposed to a steady heat for a period of from eight to nine hours. Of the total product, part is now ready for the open market without any further treat ment, a small portion of it is sent to the gal vanizing room to be galvanized and a large proportion of it goes to the nail mill to be made up into wire nails or barbed wire.