SECTION OF SHOT-TOWER.
SIEVE FOR MAKING SHOT.
Shot are made either of iron or lead. All shot for great guns or cannon are made of iron, but for small-arms leaden balls are used, which are cast to fit the bore of the weapon. For sporting purposes small shot are made, of different sizes; they consist of globules of lead with a small proportion of arsenic mixed with it—the object of mixing arsenic is to make the shot divide better, as it has been found by experience that lead alone does not divide so well—this mixture, while in a fluid state, is poured through a colander or sieve made of iron and having the bottom perforated with small holes, to suit the size of the shot to be made. These colanders are placed at the top of a high building like a tower, and the melted metal runs through the perforations in fine streams and separates into single drops as it falls. At the bottom of the building the shots are received in vessels of water, to cool them. In these vessels all the little globules are not exactly of the same size, although the holes in the colanders regulate this to a certain extent, moreover they are not all round; they have, therefore, to be sorted, which is done by placing the shot by handfuls upon a board slightly tilted, so that the round ones roll to the bottom and are received in a box, those that are crooked, &c., lag behind on the board, and are put aside to be re-melted. The shot in the box have next to be sorted as to size; this is done by means of two sieves; the holes of one sieve are a little larger than the size of the shot required, and this retains therefore all that are too large, the next has holes a little less than the shot, and this retains the right size and lets all the shot that are too small pass through; by these simple means the shot are separated into many sizes, which are numbered. The shot have now to be finished, which is done by turning them, mixed with a little black-lead, in a sort of barrel, which gives them a beautiful black shining surface, and rubs off any roughness.
FILES.
FILE CUTTING.
Files are among the most useful of tools for those who work in metals, and in many other substances, as ivory, or hard woods. A file consists of a bar of steel of various shapes, such as flat, square, three-cornered, round, and half-round; on the surface of this bar of steel small furrows are formed, with rough projections between them, and these are again, in most kinds of files, crossed with others. The mode of making a file is as follows:—A bar of wrought or cast steel is cut off of the requisite length and of the proper figure, and forged on an anvil to the required shape—that is to say, rather tapering at the top and brought to a point (called the “tang”) at the bottom, so that it may be driven into a wooden handle. The file has now to be cut. To do this requires great manual dexterity. A man sits before a bench, and passes a strap over each end of the file so as to steady it, and these are kept down with the feet. A small chisel of hard steel is held in the left hand between the thumb and finger and struck with a short-handled heavy hammer, the effect is to cut a notch, with an elevation at each side called a “burr;” the small chisel is slipped up to this “burr,” and struck again, and so on till the whole file is cut, and this with such rapidity that the eye can scarcely follow it. When the file is thus notched from end to end, it has to be hardened, which is done by making it red-hot and suddenly plunging it into cold water, which makes it so hard that it will scratch glass and cut away any other metal.
