Auxiliary lining is that which is performed upon all sorts of forgings and castings whose boundaries are quite different to those of the objects when finished. The difference is often sufficient to prevent any person knowing what the piece is intended for until distinctly informed; and the lining of such pieces is mentioned because it is effected in conjunction with planing.

Preparatory or auxiliary lining need not be very accurate, because its use is to roughly indicate the shapes of the required articles, in order to produce them by sawing, drilling, planing, or some other sort of shaping, that they may appear somewhat like the intended forms. After the first lining, another is given to indicate the precise dimensions. Of such preliminary lining a few examples are now given.

A flat cake of steel intended for a link, appears lined for drilling and shaping, in Fig. 676, and such lining is done, in this case, after the piece is planed on both broad sides to nearly the finished thickness; so that this lining is sufficient for the entire slotting and outer shaping to the precise shape and dimensions, excepting the thickness of the link, which is obtained by a final smooth planing, or filing, if such is the usual treatment.

A spindle having a rough solid portion extending from the mid part intended for a crank, like Fig. 677, is lined and dotted, as in the Figure, when it becomes ready for planing, to form the gap, if the intended gap is not too deep for the planing-machine ; or for being drilled, sawn, or slotted, if the crank is large. When this crank is thus roughly shaped, the crank-axle is lined, centred, the axle and crank-pin turned, and the gap-sides shaped, previous to finally planing the edges or narrow sides of the crank-arms. A crank-axle thus made, is also lined at the axle-ends of the arms, as seen in Fig. 678. Slotting or gap-making processes, similar to these now mentioned, are also adopted for a crank which is to have a taper gap, as shown in Fig. 679.

A single-crank axle is also made of a flat planed parallel bar, resembling Fig. 680. The dotted lines in this Figure indicate the marking for a two-crank axle ; such a piece, therefore, requires the mid part of the axle to be twisted, after the superfluous pieces are drilled off, or gradually planed off. When a parallel bar of this shape (Fig. 680) is to be made into a single-crank axle, about half the marking is sufficient, and no twisting is needed. Whether the bar is to be made into an axle with two cranks, or into one having only one crank, another series of lining processes is always requisite after shaping to the preliminary lines.

Crank-levers also, are sometimes roughly planed and lined, previous to making the holes with a boring-machine, in order to prepare them for an accurate turning and boring with a lathe ; a couple of lines for this purpose are shown in Figs. 681 and 682.

When the shaping of a tee-end and solid fork-end rod is to be commenced, the first step should be to place it upon the vee-blocks on a table, as seen in Fig. 683; and in this situation the particular shape of the forging is ascertained, and also whether it needs planing, previous to turning; but lathe-turning should in every case be the first process for such rods, unless the object is forged much too large in the tee-end and fork-end.