In crossheads of this character the lengths of the constituent fibres should be at right angles to the length of the corresponding piston-rod, and therefore parallel to the length of the crosshead itself. To obtain this arrangement it is necessary to draw down a bar of tenacious iron until its width and thickness equal the thickness and width of the largest part of the intended crosshead, which is the boss or mid-portion.

A small crosshead is easily forged at the end of a long bar, and may be completed previous to cutting off. A pair of fullers are driven in at two places in the mid-portion of the piece intended for the crosshead; the boss is then produced in the middle as required. After the boss is thus formed, the lumps adjoining are reduced by sledge-hammering to the suitable width and thickness. A crosshead-piece is shown by Fig. 143.

By this treatment the fibres are properly arranged throughout the length of the crosshead, the fibres of the boss being circularly disposed by driving in the fullers; and the fibres of the adjoining portions are retained in a position which is parallel to the length of the work, being the arrangement desired.

For a large crosshead a similar arrangement is necessary; but a difference of manipulation is resorted to, by reason of the greater weight of iron requiring to be handled. For portability, it is advantageous for the workman to know what length of metal is necessary to be drawn down to any length of crosshead that may be desired, if the forging is to be of one piece only. The engine-smith can then select a bar from a shingler who is appointed to build up the bars from pieces, or from any other forgeman whose duty it is to prepare the bars. If the smith has thus a suitable bar at command, he can commence forging by driving in the steam-hammer fullers to produce the boss; but if the bar is too long, the necessary length may be ascertained by the appropriate rule (page 8), and that which is not needed is cut from the bar at the first heat. The fullers are then applied, and the adjoining parts reduced by steam-hammering, the work being supported by endless chain and a crane during the whole of the forging.

It is not usual to forge any hole whatever in a crosshead-boss, the entire boring being done in suitable boring-machines.