These, like crossheads, are used of all lengths and diameters, and for engines of all classes. When used for small high-pressure land-engines, side-rods are at the same time connecting-rods, being connected at one end to the main crank-shaft, and the other end of the rod being attached to one end of the piston-rod crosshead.

However small the side-rod may be, it is advantageous to punch a hole into the eye or boss-part. The punching is not needed to avoid drilling, but to produce the necessary circular disposition of the fibres in the boss. For this purpose the punching is very effectual, if performed at about welding heat; after which a six-sided or eight-sided drift may be driven into the eye to shape it for the brasses when it is desirable to avoid shaping by other machinery.

After the boss and eye-part is forged, the adjoining portion of the rod is reduced by thorough hammering while at about welding heat, to produce a tough intermediate portion for the rod. The whole of a small side-rod may be forged at one end of a bar of convenient length to hold without tongs, the work being cut off at the conclusion.

Large side-rods need a more careful management to ascertain the length of metal necessary for the rod. By first distinctly stating the respective sectional areas of the iron to be used, and the rod to be made, only a sufficient length of metal need be handled, which is advantageous both for convenience of portability and economy of metal.

Side-rods are also made by another method, which consists in making two separate pieces and afterwards welding them together, the joint being in the middle of the rod. The length of iron required may be discovered in the appropriate manner, after which the eye is punched and drifted, at nearly welding heat, to any desired diameter and shape; the proper shape of the eyes in large side-rods being circular. When the two pieces are reduced to their proper diameter and increased to a correct length, the two are strongly united by a tongue-joint (Fig. 133).