After the work is suitably shaped, the thick part is formed into the crank, partly with bending and partly with chisels.

The first heating for bending is given to the lump, and also to portions of the axle ends; the work is then put beneath a hammer and across a gap which is a few inches wider than the width of the intended crank measured from one axle end across the crank to the other axle end.

The two upper corners or entrances to the gap are curved, to promote an easy bending; and, while the work is lying across the opening, with the thick lump downwards, a fuller-hammer is driven into the place of the intended crank-gap.

At the commencement of cranking, the length of the protruding fuller portion of the hammer employed need not exceed four or five inches; consequently, when the fuller has been driven in to the distance of four or five inches, the broad shoulder of the hammer will strike the two axle ends at the same time that the thin fuller portion strikes the bottom of the newly made gap, at which time the hammer will tend to straighten the work, which has become bent with driving in the fuller. The fuller is next taken out, the axle ends further straightened, if necessary, and another fuller put in, which is about eight inches in length. The fullering is resumed, the axle ends straightened as before, and another longer fuller is driven in, if necessary.

During these gap-making processes, that part of the lump intended for the crank-pin should be as nearly cold as the adjoining heated portions of the crank will allow, because it is necessary that the two arms and their junctions with the axle ends should be at nearly welding heat. It is also necessary to remember that each successive heating should be further and further from the crank-pin, and nearer and nearer to the ends of the axles, for the purpose of lengthening the throw of the crank without injuriously stretching the two lever-arms.

By such a series of fullerings, a crank of short throw, suitable for an intermediate axle, is formed in a few heats, if the thickness of axle does not exceed seven or eight inches; and for throws of any length, or metal of any thickness, the same method may be adopted, if the hammers and anvil-blocks are of sufficient dimensions.

When a crank is thus roughly formed, the crank-pin portion may be lengthened by drawing, or, if necessary, shortened by upsetting with a pendulum; any superfluous metal may be also cut off, and the two crank-arms shaped to the proper form.

The crank being finished, the drawing down of the axle ends to their diameters is next completed, the bearing parts well closed, the work cut to length, and allowed to cool slowly.

Of a crank forged in this manner two uses can be made. It may remain in its condition of a two-arm crank, or it may be divided and become a one-arm crank, having the crank-pin outside and solid with the lever. A crank made in this manner is shown in Fig. 185.

When it is intended to divide the work, the cut is made through that arm which is not required to be part of the crank. The place of the cut is in line with the edge of the thick crank-pin portion; and when the superfluous lever is cut off, the crank-pin remains already produced from the lever as intended. The place of the cut is indicated in the Figure (185) by C.

The making of an intermediate crank-axle of three pieces consists in forming, by the method described, a crank having two short axle ends, and welding them to two other pieces of any required length and shape.

• Several other processes are resorted to for producing two-arm cranks; of these methods the principal shall be described.