These are of various lengths and diameters, according to the lengths of cylinders and class of engines for which the rods are made. A few are indicated by the Figures, No. 1ll representing one for an engine having two piston-rods attached to the crosshead, No. 112.

Such rods may be made of fibrous steel, when metal of that quality is accessible. Previous to forging the rod, a piece of the steel should be subjected to a severe steam-hammering and reducing while at a bright red heat, and be drawn down to a four-sided bar about half or a quarter of an inch square. This small piece may then be further thinned on the anvil-beak, and made round instead of square. The stretching on the anvil-beak should be performed at about a foot from one end. If this thin part can be drawn to about a sixteenth without cracking, the steel is good enough for a piston-rod.

Another mode of discovering the quality is by subjecting a piece of the cold steel to a gradual tensile strain. If the steel breaks suddenly without stretching, it is not fit for a piston-rod, or any other engine-work of consequence, however great the strain may be that breaks it; but if, previous to breaking, it will stretch to a diameter which is about three-quarters of its original diameter, the metal is about as tenacious as can be expected, and may be used with confidence and advantage if it possesses the hardening properties.

If such steel is to be used for a piston-rod having a conical end, the cone may be formed by upsetting a rod whose sectional area is equal to that of the rod when forged. Steel rods should be forged so that not more than three-sixteenths is allowed for lathe-turning; they should, therefore, be carefully smoothed and straightened with rounding tools while on a surface-table, or by means of a lathe, as previously described.

Fig. 113 denotes a piston-rod having a holder at the conical end, for the convenience of holding the work while in a lathe. The holder may be made in the lathe by turning a short portion of the rod to the desired diameter, or the holder may be forged on the anvil by fullers and reducing, this being the shorter method.

Piston-rods of this character, also, may be made of fibrous steel, for the benefit of its superior wearing qualities or non-weaving qualities. The conical end is commenced by first tapering down a short portion of the end to about a fourth of its diameter. This part, being intended for the holder, is cooled after the rod is again heated for the upsetting of the cone; and after repeated coolings and upsettings, and when the cone is increased to its proper dimensions, a few pieces are cut from around the intended holder, so that drawing or stretching it may be commenced. The holder is next reduced, by fullers and hammering, till its desired form is produced. The work is next cut to its length, and finally smoothed and straightened, the proper quantity of metal being allowed for the lathe process.