Cranks are made also of two bars welded together, so that the width and thickness, when welded, shall be about equal to the thickness and width of the crank required. By this mode, the primary axle-piece may be of any convenient length, and is fitted to the intended crank in a manner similar to that described for forked levers. The difference consists in not making a separate crank-pin; this pin being part of the two bars of which the crank is made.

It is necessary that the bars be soundly welded in the parts intended for the levers and crank-pin; but the opposite ends may remain open, and will require cutting open, if the two become united during the welding. After a thorough welding, the quantity required for the crank is cut off, and the ends not welded are heated and placed upwards beneath a hammer. A narrow fuller is next driven in between the two ends, and afterwards a broader fuller is driven in, also a wedge or thick chisel, until a gap is produced similar to that in Fig. 194. The axle is then fitted to its place, and there welded to complete the crank-shaft The axle and crank are represented by Fig. 198.

Instead of thus making a crank of two bars, one may be used, if circumstances permit. When a piece of metal large enough to be formed into the entire crank, and a steam-hammer chisel big enough to make the opening, are accessible, it is advisable to use one solid piece for the crank, because in such a piece the metal for the crank-pin will be compact, and not so likely to show any joint. The shape of the axle gap in a single piece is similar to the gap in a crank made of two pieces ; the crank and axle are therefore united together in a similar manner. A solid crank-piece without a joint is shown by Fig. 195 Whether one bar or two be used for such a crank, the lengths of the crank-pin fibres are at right angles to the proper position; therefore this is an objection to the method, which should be partly remedied by making the crank-pin part as solid as possible.

By a method similar to the one last described, two cranks may be made of one bar, or of two bars welded together in the middle. In such cases, a lump is selected or reduced to proper width and thickness, and a sufficient length to make two cranks. The work is next cut into two at about midway between the ends, and the axle gaps are made with chisels and fullers, as for other cranks. When two bars are welded together for the purpose of obtaining one bar of suffi.cient thickness, the axle gaps may be formed by omitting to weld the work at the ends. The bar for making two cranks then appears as in Fig. 197.