' The best process of slitting commonly em ployed in America for grades of brass which can only be rolled cold, consists of casting the brass in the form of long bars, either square or round, from PA to 154 inches thick. Each of these bars is rolled down separately in the cold state into a rod about inch in diameter or i sometimes less, which is afterward drawn into wire. Pieces weighing from 60 pounds to 70 pounds can thus be obtained. The advantage of this process over the old one is that longer lengths are obtained and labor in the drawing is to some extent saved. A process brought out some years ago in the north of England con sisted in casting in a centrifugal mold about 18 inches in diameter and mounted on a vertical axis revolving at a high speed, so as to produce a casting in the form of a hoop. This was rolled down in open-ended rolls brought to gether with hydraulic pressure and working in the same manner as those used for rolling out the tires for locomotives and other railway stock. A large thin hoop about three inches wide resulted, which was then cut in circular shears helically, forming a long strip, and this was drawn in the usual way. The great advan tage of this method lay in the fact that a heavy piece was obtained, at the same time having a small section ready for drawing. In France a
method often employed of making the wslittings* is to roll the metal down into large sheets, which are cut into strips spirally. Another method tried in America consists in casting a solid billet, which is pierced with a suitably constructed mandril to form a cylinder, which is afterward cut up helically and drawn in the usual way.
In recent years continuous drawing machines have come very much into use. With these machines, instead of winding the wire on to a block after drawing through one die at a time, the wire is drawn through one die, then wound two or three times round a block and taken through another die, and so on, the friction on each drum being sufficient to carry the wire forward and the circumferential speed of the drums being varied to suit the elongation of the wire. Owing, however, to brass being very quickly hardened by drawing, it is not possible to carry on this process ad infinitum unless the wire be annealed periodically. When once it has been annealed it is possible to effect a very large reduction at one draught, the actual amount varying with the composition of the brass, the larger the proportion of copper the greater the reduction at one draught. See