The shaping of arms with slotting-machines is especially suited to large levers and bars. If a lever requires shaping along its arm and also around both its bosses, the bosses should be first reduced to the required dimensions by means of an arbor-chuck, or while fixed on other packing as before described, using the rotary motion of the worm wheel. The lever is next fixed for the purpose of shaping its narrow sides, with one or both bosses in contact with parallel packing on the table, and so that its length is nearly parallel with the machine-front, and consequently, nearly parallel with the traverse of the rest which is parallel with the machine-front. If it were intended to make the arm parallel, as for a connecting-bar, the arm's centre length would be adjusted exactly parallel with the traverse; but to obtain the taper form required for a lever, it is so placed that the side or surface to be produced, is parallel with the traverse referred to. To ascertain whether the object is properly placed, one of the straight gauge-lines on the table should be used as a species of standard to which the gauge-line that shows the quantity of metal to be cut off, is put parallel. For this purpose, a scriber-block having a straight bottom edge, is stood upon some part of the table's gauge-line, and the scriber-point is adjusted to one end of the line on the lever; after which, the block is removed to the opposite end of the lever and stood upon another part, of the same gauge-line on the table. The scriber-point is now observed to discover how near the line on the lever is to parallelism with the line on the table, and therefore, how much shifting of the lever or bar is necessary to adjust it. When the piece has been moved a short distance, the scriber-point is again referred to as before, and another shifting is effected, which processes are continued until the object is properly placed.

As soon as the lever's gauge-line is adjusted to parallelism with the gauge-line on the table, and the piece properly fastened with plates and bolts, the lever is advanced to the cutting tool and the shaping of the arm's narrow side commenced. At this time the tool is at one end of the arm, which is the curved junction with the boss. The shaping progresses by the up-and-down motion of the tool, and the movement of the lever in the direction of its length, or rather in the direction of the gauge-line showing the place of the plane to be produced. By reason of this line being parallel with the gauge-lines on the table, the surface formed by the process of shaping must be also parallel with the gauge-line on the lever, because this line was put parallel with the table's lines, and these were marked with the same traversing motion of the rest which is now used for advancing the object during shaping. Concerning the marking of these lines upon slotting-tables, refer also to pages 269 and 270.

When the lever or bar is to be advanced to the tool to commence the shaping, or to take off another slice after the piece has been once advanced across the tool, the movement of the slide-rest screw causes the lever to move sideways. This is the direction in which it moves each time it is adjusted for having a slice removed, the movement being effected with the screw which is at right-angles to the machine-front, and at right-angles to the length of the lever. Immediately after this screw has put the piece to the place required, the screw is fixed to prevent unintentional shifting of it during the cutting; the cutting being executed by the rotation of the other screw which is parallel with the length of the lever-arm. The traverse performed with this screw is the only motion required besides the up-and-down action of the tool, to execute the entire shaping. If it happens that a large amount of metal is to be cut off, several travels of the lever in the direction of its length may be requisite, the amount removed each time, depending on the power of the machine. The quantity cut off during any one advancement, is named a slice; and the entire amount removed to reach the gauge-line, is termed the krap. A strip or cut, is the quantity cut off during only one downward travel of the tool. These various amounts of metal are analogous to those cut off with planing-machines ; and the terms which represent them are given in the chapter on planing and lining, at pages 215 and 216.