The final adjustment of all sorts of crank-shafts includes straightening the axles, and placing the centres of the two crank-pins at right angles to each other. The entire adjustment can be effected while the shaft is either entirely supported by the anvil, or partly supported by the anvil at one end, while the other end is in the gap that was used for twisting. To ascertain the amount of adjustment necessary, an iron template is made, having two arms at right angles to each other, representing the two cranks. This template or gauge fits the intermediate portion of the axle, and, being portable, is easily applied.

To rectify a shaft without such a gauge, it is necessary to put the shaft upon a table of sufficient length; and in many cases such a table is not accessible; hence the convenience of a portable gauge.

To straighten the axle, the anvil having the largest face that the framing will admit should be put into position ; and the face of the anvil should be concave to the extent of about half an inch or an inch at the middle. To indicate the part of the work which needs a blow, a wooden iron gap-straight-edge, or straight-edge of wood only, is supported at different sides of the axle by three or four men while the smith walks along and observes the distances between the straightedge and shaft at several places throughout its length. He then measures the distances with inside callipers having a long handle, if the work is hot enough to require it. And when the differences of the distances between the straight-edge and shaft are thus discovered, the concave parts or hollow parts of the axle are also discovered; these parts are then put next the anvil-face and a few blows given ; after which the straight-edge is again supported and applied to the work by the men, to ascertain if the axle has been improved with the hammering, and which part is next to receive a few blows.

By means of a long gap-straight-edge thus handled, or by means of a large surface-table, the crank-shaft can be adjusted while it is still hot at the conclusion of forging, and previous to putting it into a lathe. The gaps in the straight-edge are to admit the fulcrum ends of the cranks that extend beyond the axle sides ; the gaps should therefore be five or six inches deep ; by this means the straight-edge can be put close to, or near to, the axle throughout its total length.

When it is considered inconvenient to make a long gap-straight-edge, the axle must be put into a lathe to ascertain the places of the bent portions, because short straight-edges are of little use for work of great length. During the application of the straight-edge to a shaft of great length, the work requires supporting at several places to prevent it bending through its own weight.