Weigh-shaft levers are usually forged of tenacious iron to facilitate the fitting of them to their shafts. In some cases the levers are tightly fixed by making them hot and shrinking them while in their precise situations on the shaft. In such cases, the contraction of the boss would have a greater tendency to tear it asunder, if made of steel, than if made of iron.

The necessary strength of the boss is obtained either by adopting a long boss of short diameter, or by a short boss of long diameter; these bosses are made by doubling or trebling a bar at one end, and thoroughly welding the layers together, and then punching and drifting the opening or orifice to the required diameter, which produces the desired circular disposition of the fibres in the boss. After which a welding heat is again given to the boss, and it is shaped by a sledge-hammering equally administered around the boss, while it is upon a cylindrical filler, similar to that mentioned for strap-shaping. This hammering is needed to produce a tough fibrous boss. After the boss is thus made at the end of the work, broad fullers are driven in to reduce that portion next to the boss ; the adjoining part is then reduced to the shape of the lever arm, and a piece is allowed to remain, which is of sufficient dimensions to be formed into the smaller boss at the other end of the lever. The next operation is cutting the work from the bar, and making the smaller boss, either by doubling or trebling if necessary. When both the holes are made and drifted, and the outsides of the bosses well hammered, they may still be too large; if so, a trimming-chisel is used to trim the bosses to their respective dimensions. The bosses are finally flattened, and also smoothed with curved rounding-tools, whose gaps are of suitable width.

Weigh-shaft levers are also made by reducing the ends of two bars, and welding the reduced portions together. By this method, all doubling or trebling to make the bosses is avoided. But, after being punched, they require the same welding, drifting, and hammering as other bosses, for producing the circular arrangement of the fibres. This mode of drawing down to produce half the lever arm from each boss is economical for all kinds of short levers, because only a small amount of reducing is necessary to attain to the length desired; but for long levers, whether large or small, the plan is not adopted without making two joints for each lever. By this means, a piece which is of the finished forged width and thickness is welded into the two stems which were reduced from the bosses.