Secondly, by jumping: - A piece of bolt-iron of five-eighths of an inch diameter, or of the size of the stem of the bolt, is cut off somewhat longer than the intended length; "a short heat" is taken upon it, that is, the extreme end alone is made white-hot, then placed perpendicularly upon the anvil, and the cold end is struck with the hammer as in driving in a nail; this thickens the metal or upsets it, and makes a thick conical button. The head is completed, by driving the bolt into a heading tool with a circular hole of five-eighths diameter; the thickened part of the head prevents the piece from passing through, and the lump is flattened out by the hammer into an irregular button or disk, which is afterwards beaten square to complete the bolt. Figs. 99, 100, and 101, explain these processes; the latter is a single tool, but the heading tool, fig. 102, with several holes, is also used.
In upsetting the end of the work, if more convenient, it may be held horizontally across the anvil, and struck on the heated extremity with the hand hammer; or it can be jumped forcibly upon the anvil, when its own weight will supply the required momentum. If too considerable a portion of the work is heated, it will either bend, or it will swell generally; and therefore to limit the enlargement to the required spot, should the heat be too long, the neighbouring part is partially cooled by immersing it in the water-trough, as near to the heat as admissible.
Thirdly, the same bolt may be made by building up or welding: - An eye is first made at the end of a small rod of square or flat iron; by bending it round the beak iron, as in fig. 103, it is placed around the rod of five-eighths round iron, and the curled end is cut off with the chisel, as in fig. 104, enough iron being left in the ring, which is afterwards welded to the five-eighths inch rod to form the head of the bolt, by a few quick light blows given at the proper heat; the bolt is then completed by any of the tools already described, that may be preferred. A swage at the angle of sixty degrees, fig. 105, will be found very convenient in forming hexagonal heads, as the horizontal blow of the hammer completes the equilateral triangle, and two positions operate on every side of the hexagon; fig. 105 is essential likewise in forging triangular files and rods.
Of these three modes of making a bolt, and which will apply to a multitude of objects somewhat analogous in form, the first is the most general fur small and short bolts; the second for small but longer kinds; and the third is perhaps the most common for large holts, although the least secure; it is used for bolts for ordinary building purposes, but is less generally employed for the parts of mechanism.
For works of the same character, in which a considerable length of two different sections or magnitudes of iron are required, the method by drawing down from the large size would be too expensive; the method by upsetting would be impracticable; and therefore a more judicious use is made of the iron store, and the object is made in two parts, of bars of the exact sections respectively. The larger bar is reduced to the size of the smaller, generally upon the beak iron with top fullers, and with a gradual transition or taper extending some fes inches, as represented in fig. 106; the two pieces are scarfed or prepared for welding, but which part of the subject is for the present deferred, in order that the different examples of welding may be given together.
The figure 106 is also intended to explain two other proceedings very commonly required in forging. Bars are bent down at right angles as for the short end or corking of the piece, fig. 106, by laving the work on the anvil, and holding it down with the sledge hammer, as in fig. 107; the end is then bent with the hand hammer, and trimmed square over the edge of the anvil; or when more precision is wanted, the work is screwed fast in the tail-vice, which is one of the tools of every smith's shop, and it is bent over the jaws of the vice. When the external angle, as well as the internal, is required to be sharp and square, the work is reduced with the fuller from a larger bar to the form of figure 108, to compensate for the great extension in length that occurs at the outer part, or heel of the bend, of which the inner angle forms as it were the center.
The holes in fig. 106, for the cross bolts, arc made with a rod-punch, which is driven a little more than half way through from the one side whilst the work lies upon the anvil, so that when turned over, the cooling effect of the punch may serve to show the place where the tool must be again applied for the completion of the hole; the little bit or burr is then driven out, either through the square hole in the anvil that is intended for bottom tools, or else upon the bolster, fig. 109, a tool faced with steel, and having an aperture of the same form and dimensions as the face of the punch.
216 SQUARE AND HEXAGON NUTS, ETC.; PUNCHING.
Fig. 112 shows the ordinary mode of making the square nuts for bolts. A flat bar is first nicked on the sides with the chisel, then punched, and the rough nuts if small, are separated and strung upon the end of the poker (a slight round rod bent up at the end), for the convenience of managing them in the fire, from which they are removed one at a time when hot, and finished on the triblet, fig. 113, which serves both as a handle, and also as the means of perfecting the holes.
For making hexagon nuts, the flat bar is nicked on both edges with a narrow round fuller; this gives a nearer approach to the hexagon: the nuts are then flattened on the face, punched, and dressed on the triblet within the angular swage, tig. 105, page 214, before adverted to. Thick circular collars are made precisely in the same way, with the exception that they arc finished externally with the hammer, or between top and bottom rounding tools of corresponding diameter.