A lever, or other article having a boss, needs more consideration previous to lining and planing, than such a simply formed object as a straight rod or bar; and the more irregular, or the greater the number of dimensions of any object, the greater is the amount of consideration requisite.

Solid bosses, without any hole, are, for some sorts of work, forged singly, each having a short arm, or two arms, extending from the boss, for welding to the remaining portion of the work after the boss has been bored, turned, and planed. A boss of this class, having one arm, is denoted by Fig. 663. The lining of such a piece commences with making a primary dotted line along the arm, as seen in the Figure; and before this line can be properly placed, the operator must refer to the sketch of the finished dimensions, or ascertain by some means the required length of the boss, and the required thickness of the arm. When these are known, the rough piece of work is measured, to discover which portion is nearest to the desired finished size, the arm or the boss. If the arm is found to be only a sixteenth thicker, and the boss a quarter of an inch longer, the primary line is marked along the middle of the arm, without caring whether the line will pass through the middle of the boss. But if the boss is nearest to the finished size, the mid-length of the boss is the place for the line, without regarding the situation of it along the arm. From the primary line, however placed, the length of the boss should be measured in both directions, because it may be necessary to make the boss extend further from one side of the arm than from the opposite side. Marking the length of the boss by this means prepares it for boring and turning, and also shows whether the arm requires reducing more at one side than at another.

If a boss and arm of this sort were properly forged, the arm is that which is smoothest and nearest to the finished dimensions; in this case, the arm is laid flat upon a right-angled block or blocks on a planing-table, or on a lathe-chuck, and the boss made parallel to the arm, without any previous planing being required. In addition to placing a line as in Fig. 663, a line is also made along the middle of that side of the arm and boss-face shown in Fig. 664. This line will show whether the boss is in line with the arm by scribing a circle on the boss-face with the straight line as a centre. If the boss is thus found to be out of its proper place, the metal will be lathe-turned from the proper side, because the boss will be adjusted for boring by means of the scribed circle, and not by the rough outline of the boss.

Fig. 665 denotes a boss having two arms, and such a piece is lined and adjusted with the same considerations as if it had but one arm, but with the additional necessity of making the dotted primary line along both arms; and if planing is intended, the parallel blocks are put beneath both arms. Fig. 666 represents a boss having two arms, which are either forged to the proper dimensions, or have been planed thereto; consequently, the piece is lined along the middle of both arms and the boss-face, to allow a circle to be scribed, to which the work is adjusted while fixing for boring and turning.

When a complete lever is forged, with all its bosses, as denoted by Fig. 667, and both arms are properly forged, it is fit to be placed upon parallel blocks which are in contact with the lever-arms, that the bosses may be bored, reduced to length, and the outsides of the bosses shaped, by means of two primary lines, one to get the centres of all the bosses' faces, as shown in Fig. 667, and the other primary line to adjust the arms, and to mark the lengths of all the bosses, which line is the dotted one seen in Fig. 668.

The connecting bar shown by Fig. 669 has a dotted line along the middle of one side or edge of the arm, to allow the length of each boss to be marked ; and a similar bar is shown by Fig. 670 to be lined along the middle of its broad side, to find centres for the bosses, that they may be so bored and turned as to be in line with the arm or intermediate part when finished. The marking of both these lines is in accordance with the remarks given concerning other bosses.

All the scribing processes just given may be easiest performed by means of right-angled blocks, which are to be placed beneath all the arms referred to, in the situation represented in Fig. 671, standing on the face of a table. Whether the object is a single-arm boss like Fig. 663 or 664, or a two-arm boss like Fig. 665, or a lever with three bosses similar to Fig. 667 or 668, the scribing is done with a scriber-block being moved entirely around the object while it rests on the blocks. By this marking, a sort of periphery is scribed upon two opposite sides or edges of the arm and the boss at one scribing. Either one block or two are required, according to the length of the arm and size of the blocks; and any boss-arm, lever, or bar may be placed on the blocks for lining, in any of the positions shown, whether as in Fig. 663 or 671; or in the position termed edgeways, as in Fig. 667 and 670. In order to adjust the scriber-point to the height for each line, the point is put as near to the middle of the surface as can be judged, and a short line marked ; the object is next put upside-down upon the same block or blocks, and another short line made without altering the height of the scriber. The point midway between these two marks is the desired centre, and to this the scriber-point is carefully adjusted, and the primary line scribed entirely around the work, bosses included, by moving the block around as directed.