The variety of strap denoted by Fig. 25 is used for connecting crank-pins with connecting-rods; also beam gudgeons with side-rods and connecting-rods.

The proper arrangement of the constituent fibres is obtained by bending the straps from straight bars which were previously welded and reduced to a suitable width and thickness.

Those portions of the arms which are indicated in the Figure by A are thicker than the adjoining portions, because the key and gib-way detracts from the strength of the arms.

The thicker portions of the arms are made by doubling the piece at each end, and welding by good steam-hammering; after being welded, and while being reduced to the thickness, the part intended for the semicircular portion is allowed to remain a little thicker, to compensate for waste while being heated several times for bending, and also for stretching.

The bending or curving is effected by heating the intermediate portion to a length which is equal to the entire length of the curve required in the strap. It is then bent by placing one end into a slot in a heavy block, and pulling down the opposite end ; after which, the two arms of the strap are flattened and smoothed by placing a filler into the mouth or opening, and hammering the outsides.

Straps of great weight and dimensions are bent by long and strong levers, which have gaps or openings at the ends, one end of the strap being gripped by the lever while the bending is effected. Several heatings are necessary, the precise number of which depends upon the thickness of the work, the quality of the implements employed, and the promptness with which the power is applied.

The fillers for shaping the curved parts are made of cast iron, and of various dimensions to suit various sizes of straps. Each filler has a wrought-iron handle, which is fixed by the iron being poured around one end of the handle, at the time of casting the filler. Another class of filler also is used for shaping, and consists of a piece of cylindrical iron or steel, which is supported at each end by two heavy cast-iron blocks. On the upper side of the blocks are two angular gaps, into which the two ends of the cylindrical filler are placed. The distance between the two blocks is only sufficient to allow the two arms of the strap to hang freely while the curved part is supported by the piece of round iron, the ends of which are in the two angular gaps (Fig. 142).

Round iron of any suitable diameter may be selected as a bearing for the strap ; and, while thus supported, either of the two arms may be gripped by tongs, and any part of the bent portion may be stretched, flattened, smoothed, or adjusted.