A crank-pin, having a screw for a nut, is shown by Fig. 114, and another class of pins, for use without nuts, is indicated in Plate 4.

Plate 4

The forging of a crank-pin principally consists in well closing the metal in those places intended for the friction part and the screw, if a screw is to be used. All the other parts of a crank-pin should be fibrous.

The angle subtended by the two sides of a crank-pin cone should be less than that of a piston-rod cone; so that a crank-pin requires no upsetting, the iron or steel selected being large enough for the largest end of the cone.

For a pin whose largest end of the cone is to be outwards, a holder is sometimes made resembling that in Fig. 113, for the convenience of holding while being turned.