In an excentric-rod, represented by Fig. 36, the mouth or orifice indicated by 0 is usually cut while cold by slotting, the rod being forged solid at both ends, although a gap is shown in the Figure, which should be the case with any sketch or drawing by which the smith may be working. He will then exercise sufficient care to arrange the fibres, that they may be in a suitable shape and position after the mouth or gap is cut.

The two ends of such a rod are first forged separately, each piece having a stem with a good scarf for welding to the intermediate portion of the rod. To form the gap end or fork end, a thick bar is doubled at one end and welded together. The length of the doubled part is sufficient to extend a considerable distance into the stem that is to be scarfed, to prevent cracks being formed at the inner curves of the boss.

Another method of making a good fork-end consists in welding and reducing a bar to the outer dimensions of the fork or fork-piece, and then driving in a fuller at the inner extremity of the solid or boss part of the intended fork. After the boss is thus produced by a fuller, the adjoining stem is reduced to its width and thickness and increased to a convenient length for welding to the intermediate piece, a lump being allowed to remain to avoid upsetting for scarfing.

In a fork-piece thus made, the orifice may, if necessary, be formed by first punching a round hole at the inner extremity of the intended opening, and afterwards cutting out with a chisel. The chisel is driven from both sides half way through the work, and every semi-detached piece is cut out previously to smoothing the inside, which is performed by placing a filler into the opening and hammering the outside. The filler is made of soft steel and to the shape of the opening desired. While this kind of filler is in use, the outer end is in a gap-stop, to avoid being shaken out by the hammering. A gap-stop in the square hole of an anvil is shown by Fig. 77.

After the fork-piece is made, the T-piece is formed for the opposite end of the rod, which is similar to that indicated by A in Fig. 37. A good arrangement of the fibres in the T-piece is obtained by punching a large hole into a bar of good soft iron or steel, and afterwards splitting open the end by cutting a slit to meet the round hole, the hole being at a proper distance from the extremity. When the two ends thus produced are separated and properly bent to a right angle with the bar, the lengths of the fibres will be at right angles to the bar, and, consequently, at right angles to the stem, -which is to be welded to the intermediate portion of the intended rod; and this disposition of the layers and fibres is that which is necessary for strength in the T-piece.

After the T-piece is tolerably shaped, it is cut from the bar with sufficient length to be formed into a stem and scarf; and when cut off, the stem is produced and the scarf formed for welding.

The intermediate part is then made of a suitable width and length to complete the forging of the rod. The width and thickness of the intermediate piece is rather greater than the required forged width and thickness, for the convenience of stretching or drawing the rod to its exact length at the conclusion of the forging; consequently, the length of the piece is shorter than the finished length. After the three pieces are welded together, the rod is hammered to the precise length, which is measured from the centre of the fork-eye, or hole, to the centre of the T-piece, or its extremity.

While lengthening the rod to its exact length, a simple variety of gauge is made use of to ascertain the precise amount of stretching which is necessary. Such a gauge is made of a thin bar of 1/4-inch iron, the width of which is at least 1 or 11/2 inches. Ten or twelve inches at each end of the bar are tapered, and afterwards bent edgeways to the bar and at right angles to it, which produces the form of a bracket, thus; the distance between the two extremities being the length of the excentric rod. These two pointed ends are filed to a circular form, and to half a millimetre in diameter, which is much too large for other work, but small enough for forging an excentric-rod. The mode of adjusting the gauge to its exact length consists in opening or closing the two legs of the gauge until the distance between the centres of the two circular extremities is the distance desired.

Fig. 38 represents an excentric-rod for oscillating and other classes of paddle-engines. In the Figure, the gap is indicated by G, which is intended for the gap-pin. In one particular, the forging of such a rod is similar to the forging of other excentric-rods ; the rod being forged of three pieces, which are welded together at the first forging, or afterwards, when the engines are in the ship, as circumstances may require.

The forging of the T-piece is similar to that mentioned for Figs. 36 and 37. The forging of the gap-piece is performed with a piece whose width and thickness are sufficient to make a solid lump for the gap-boss. A fuller is driven in at each extremity of the intended boss, and the two straight stems are then reduced to a suitable width and thickness for the intermediate portion; a larger piece remaining at the extremity of the boss-piece for scarfing. If the stem of the gap-piece is to be turned in a lathe, a lump is allowed to remain at the taper end, instead of reducing the whole of it to the thickness when finished. Both of the extremities of the gap-piece stems are made square and solid, to conveniently admit the centring process previous to turning. No cutting or punching of the gap-piece is necessary, because it is afterwards bored while cold.