Shaping.—Thin metal is shaped by pressure applied by means of a screw press, the metal being placed between a die or mould and its counterpart.
Automatic Machinery.—A number of articles produced from wire, such as pins, nails, hooks and eyes, hair pins, etc., are made completely by automatic machinery, the wire being wound off a reel at one end of the machine and transformed into the various articles as it passes along until it comes out at the other end of the machine, a finished or nearly finished article.
Automatic Turning and Shaping.—Gun stocks, boot lasts, tool handles and other similar articles are automatically turned. With a gun stock for example, the rough form cut from a plank is put in a lathe, above is placed a steel model or dummy of the form required to be turned, the model and the wooden blank are made to revolve at precisely the same speed, and a rotating cutter travels slowly along from one end of the blank to the other, the movement of the cutter inwards or outwards being regulated by the dummy. The wooden blank having been put in the lathes, the cutting is started, and it then goes on until finished, when the lathe stops automatically. The shaping of gun locks and many other parts of the gun is effected by causing a revolving cutter to be moved over a fixed steel model or dummy, the cutter thus shapes the blank to a fac-simile of the pattern or dummy.[50]
Spinning.—Tea pot bodies and a variety of articles in Britannia metal are “spun.” A piece of wood 4 or 5 inches in diameter is attached to the lathe head, and in this a hollow corresponding to the bottom of the tea pot is turned. A sheet of metal of a foot or so diameter is now put against the wood and pressed into the hollow by a wooden cylindrical mould with a round base which corresponds to the concavity. The disc is rotated very rapidly and the workman presses the soft metal over the mould so as to form a vessel in shape somewhat resembling a coffee cup with upright sides, the cylindrical mould is taken out and replaced by a disc of wood in two halves, held in place by a spindle from the back centre of the lathe. The metal cylinder is now gradually closed in until the opening is reduced to the required size, when the body is complete. The spindle is withdrawn and the divided disc of wood easily shakes out.
Drawing Through.—Umbrella ferrules, pencil cases, cartridge cases, and a variety of articles are made by “drawing through.” The finest example of this process is seen in the manufacture of a metallic cartridge case, such as is used in the new Enfield-Martini rifle. I am indebted to Mr. T. R. Bayliss, Managing Director of the Birmingham Small Arms and Metal Company, for the following particulars. The brass is rolled to the required thickness.[51] It is then passed into a machine which forms it into a shallow cup. This machine consists of a tubular punch which cuts out a disc of 1.25 inch diameter, immediately upon which a solid plug passing through the tubular punch, presses the disc through a steel ring, so that it falls to the ground as a shallow brass cup. Three of these are produced by one blow of the press. The cups are heated in a muffle to a red heat, then dipped in dilute sulphuric acid to remove scale, washed, coated with soap and oil, and then passed through a second machine in which a slightly narrower punch forces the cup through a slightly narrower ring, and thus the cup, while retaining the same thickness at the bottom, is made slightly narrower and much deeper. Repetitions of the process (six altogether) produce a case rather more than half-an-inch wide and three inches long, which, when cut off to proper length, indented at the bottom for reception of the cap, and some other finishing processes gone through, is ready for the charge of powder. The process is applied to small articles like pencil cases, and at the Small Arms and Metal Company to cases as large as 5·20 inch diameter and 15 inch long.
Soldering.—Hard soldering or brazing consists in fusing an alloy of high melting point between two junctions of the metal to be soldered so as firmly to connect them. The solder in fine powder is mixed with powdered borax, and made into a puddle with water, and then spread about the parts to be soldered together. The article is now heated by fire or gas, and the moment when the solder runs, is carefully watched. Gold and silver soldering used in the jewellery trades is on a small scale similar to brazing, the solder used is a gold or silver alloy of slightly lower melting point than the article to be soldered: the borax is commonly applied by previously rubbing down a crystal on a piece of slate and the white puddle thus obtained applied by means of a camel hair pencil to the junction on which the solder is placed. The article is supported on a piece of pumice stone and the necessary heat produced by the flame from a mouth blowpipe. In soft soldering an alloy of tin and lead is used, the melted alloy being spread by means of a “bit” or “doctor,” consisting of a piece of copper attached to an iron rod set in a wooden handle. A flux called “monkey” or “spirit,” consisting of muriatic acid with dissolved zinc, having previously been applied. Formerly resin was used as a flux, but this is now to a great extent superseded by the mixture just spoken of.
Scratch Brushing is used to produce a rich rough surface previous to gilding. Revolving brushes of brass wire scratch the surface of the article which is kept well moistened with stale beer or with water to which size has been added.
Of late years the SAND BLAST has been introduced for roughing surfaces. Sand is fed into a powerful blast of air, and a fine frosted surface produced. If the article is protected in places by a mask of paper or soft metal cut out in any desired pattern, an ornamental pattern is produced requiring only a little chasing to finish it. The sand blast is used too in the production of an imitation of engraved glass, in embossing glass as a substitute for hydrofluoric acid, and for re-cutting old files.
Dipping.—In order to clean brass articles, they are dipped into a mixture of nitric and sulphuric acids, the temperature and strength of acid determining whether the dipping is bright or dead. The bright articles are now finished by burnishing or polishing, and are then ready for