Broad sides of arms belonging to levers and connecting-bars are shaped either by planing or slotting. It is, however, always requisite to shape the curved junctions with the boss-ends, by using some class of rotary movement, because these junctions cannot be formed with any rectilineal motion. After a bar has had its bosses bored, turned, its short boss-ends also turned, and short portions of the arm immediately adjoining also turned, the broad sides can be easily shaped by a planing-machine, whether small or large. A lever with these junctions shaped, and situated on a planing-table, is shown by Fig. 747; in which position it can be easily planed to cut off the lump on the middle ; because, by reason of the ends of the bosses having been finished by turning, and their junctions with the broad side also turned, the planing-tool is allowed ample room to cut near the bosses without touching them

It is sometimes necessary to reduce the broad side or sides of a lever while it remains on a slotting-table; the lever having had its bosses, curved junctions with the narrow sides, and the straight parts of the narrow sides just now shaped on the same machine. And it is, in many cases, convenient to shape broad sides by slotting, to avoid removal of heavy pieces to other machines, also to avoid waiting for a planing-machine to be disengaged, and as a necessity, when a planing-machine is not available.

If the lever which is to have its broad sides shaped by slotting has had the junctions with the broad sides shaped by boring and turning on a previous occasion, it can remain on the table and be shaped; if not, it must be removed, and the junctions properly formed. The arm at these places is always reduced by the rotary shaping until it is of the exact finished thickness required; consequently, it is by these smoothly formed junctions that the arm is to be adjusted, rather than to the scribed lines.

The first placing of the lever for the shaping of its broad sides consists in putting one broad side at right-angles to the slotting-table, because this is the direction of the slotting-tool's motion. If the bosses have been properly formed, their outer surfaces are now parallel with the lengths of the holes; consequently, if these outer surfaces are put into close contact with the table, or with parallel packing thereon, the lever is, by the same act, put into one of the positions required, without further adjustment. If the two bosses of the object were of the same diameter, the centre length of it would now be parallel with the table; but through one boss being smaller, the centre length is lower at one end than at the other, which is of no consequence for this shaping, because only the straight part of the side is to be reduced. Although it is not requisite to place the centre length parallel with the table, it is quite necessary that the gauge-line on the upper narrow side, showing the boundary of the plane, should be put exactly parallel with the traverse screw which is parallel with the machine-front; or rather, parallel with the direction of the traverse-slide's motion, in order that the movement of the lever during shaping shall produce the broad side in its desired condition of parallelism with the gauge-line. If this line exactly coincides with the already finished junctions, either the line or the junctions may be referred to while adjusting; the finished surfaces being always considered rather than the scriber-marks. To adjust the lever to this position a scriber-block is stood upon one of the straight lines on the table, and the point is placed for observation to both ends of the line on the lever, or to its junctions, in a manner similar to that described for other adjustments.

As soon as the broad side is put into the required position, and the lever is tightly held with plates and bolts, the reduction of the metal proceeds in a very easy manner, a point-tool like Figs. 787 or 794 being in the tool-clamps while the lever is advanced in the direction of its length by the rotation of the traverse-screw. This operation is quite as simple as if it were done with a planing-machine, and consists in producing the hidden plane by means of the vertical motion of the slotting-tool, instead of by the horizontal movement of a planing-table.

When one broad side is produced, the object is put upside-down, and the opposite broad side is thus placed in front of the slotting-tool. The lever is now fixed with the same regard to the finished junctions or gauge-line that was bestowed during the adjustment for the previous shaping; after which the removal of the metal proceeds as before.

It may now be seen by reference to the foregoing sections on the shaping of arms and bosses in general, that if the entire outer surface of a small lever or bar needs reducing, the entire shaping can be done on a to-and-fro shaping-machine if the object has been properly bored and the ends of its bosses turned; and it is also seen that a large lever or bar that has been in a similar manner properly turned can be entirely completed on a slotting-machine, which machine will reduce and correctly finish the entire cylindrical surfaces of the bosses, their curved junctions with the narrow sides, and the four straight sides of the arm whenever it may happen that such an extensive reduction is requisite. And it may be here mentioned that thousands of levers and bars are at the present time thus entirely machined while cold, although it must be admitted that if greater care were exercised during the forging of such objects, the only machining which they would require while cold, would be boring the holes, turning the boss-ends, and slightly paring the junctions. Even less paring than this would suffice for those that were forged in pressing-moulds, concerning which, and also concerning other considerations during accurate forging, refer also to pages 1, 3, 4, 30, 32, 33, 77, 78, 87, 88, and 97.