If a lever-arm is to be shaped with a planing-machine, the bosses are first bored and faced, and their ends also shaped, previous to planing, to allow the levers to be adjusted on the table by means of the smoothly finished parts, similar to the mode for adjusting connecting-bars. If the lever is a crank-lever with two bosses, it is fixed to a planing-table by bolts in the holes of the bosses, and plates on their faces, as denoted in Fig. 747 ; and if the lever is large, one or two poppets also are required at opposite sides of the arm. Packing pieces are not required beneath the arm, through its comparative thickness; but the smaller boss may need packing up with parallel blocks, which are shown in the Figure at each side of the bolt With which the boss is held. While thus fixed, the upper side of the arm is reduced to the required dimension ; after which, the lever is put upside-down and the opposite side planed. It is now ready for marking, and the marking is done upon the two planed surfaces, in order to shape the other two sides of the arm. The bosses also are sometimes shaped by planing, in which case the lever is held with its boss in contact with an el-chuck.

Levers having three bosses each, are treated in a manner resembling that for crank-levers, the broad sides being first planed, and next scribed, in order to plane the edges. At this fixing for planing the edges, the bosses also are shaped, and if the lever is small, having bosses only about two or three inches in diameter, the curved shape of the bosses is easily obtained with springy tools having concave cutting edges. Tools of this class are applied with soapy water after the boss has been roughly reduced with facers and corner tools. It may also be mentioned that the outer cylindrical surfaces of lever-bosses in general, whether small or large, can be shaped with ordinary planing-machines and planing tools, if the machine employed is strong enough, and its table is wide enough to allow the lever to be placed with its length across the table.