Fig. 118 represents a lever for an ordinary oscillating engine having two slide-valves. The making of such a lever is conveniently managed, and good work produced, by forging it of one piece.

The thickness of the lump selected is rather greater than the length of the gudgeon-boss, G. Fullers are first driven in at each side of the intended boss; the adjoining lumps are next reduced to a proper width and thickness, allowing a thick lump at each end, which is amply sufficient to be formed into the two smaller bosses without upsetting.

During the thinning of the two arms or ends • the work remains straight; so that it is needful to know the necessary length of straight iron to be formed into the required cranked arm.

The readiest mode of ascertaining the length of this arm is by making use of the full-dimensioned outline of the bent or cranked side of the lever, this outline being that to which the smith is working. A wheel measure is held in one hand, and driven along the middle of the arm or arms on the table; and the distance thus indicated by the instrument is the length of the required cranked arm, and also the length of straight iron necessary, if the straight arm at the time is reduced to its finished forged width and thickness. But the proper mode is to bend the arm while it is rather thieker and shorter than required to be when forged; so that, after being bent, it can be thinned and stretched to its proper length.

Bending or cranking commences by first making that bend which is to be nearest to the gudgeon-boss. During the first bending the lever is laid a few times to the sketch on the table, to discover if sufficiently bent or angled, or if the work were heated in the proper place.

After being heated and bent a sufficient number of times to place the angle or curve into its desired shape and situation, the work is cooled, or allowed to cool, and heated at the place for the next curve, being careful to keep the whole of the lever cold except the part in course of bending.

When all the cranking is completed, the three bosses are shaped by welding and trimming, until the three lines passing through the centres of the bosses are parallel to each other. This parallelism is known by the sides of the bosses being parallel to the boss lines when the lever is put to the sketch on the table.

Cranked levers of this class are made also by welding together three pieces.. By this mode the middle boss is separately prepared with the short arms or ends for welding to two other pieces intended to complete the lever. By adopting this method, little or no bending is incurred after the work is welded together. The necessary angling is easier accomplished previous to making the joints. A cranked lever in three pieces is shown by Fig. 157.

The bosses of all such cranked levers as we are now considering are forged solid, so that no punching by the smith is necessary.

Crank-Shaft Levers (L, Fig. 122). - The precise mode of forging one of these depends upon the weight of the intended lever, also upon the relative proportions of any one lever ; whether the mid-portion is to be long or short, and whether the bosses are to be comparatively large or small.

All crank-shaft levers should be made of soft, tenacious, new, puddled bar-iron, without any mixture with old scrap ; although new, puddled scraps may be admitted, if they be first made into the form of bars.

Whether the lever is to be a very small one, or one of great weight, it is desirable to forge it so that the lengths of the fibres in the arm shall be parallel to the length of it; and that the lengths of the fibres in the boss shall constitute a number of rings, whose centre is the centre of the hole in the boss, and named the eye.

This arrangement is easily produced in the forging of a lever whose weight is a few pounds by doubling two straight bars, and welding the four ends together, the weld being made in the middle of the lever or arm. The width of one of these two bars is equal to the length of one of the bosses, and the width of the other bar is equal to the length of the other boss. The thickness of both bars may be about 11/2 times the thickness of the intended metal around the shaft or crank-pin.

When two such bars are curved to the forged diameter of the required bosses, the holes in the bosses thus formed will be small enough to admit of boring to the finished diameters. In some cases it is more convenient for boring to fill up this hole that remains, which is done by roughly welding in a plug to make the boss appear as if solid. In other cases the small hole which is formed by bending is useful for fixing, and is therefore allowed to remain.

The first welding, after the boss is roughly formed, is performed at the boss itself, and is managed by placing the work between a pair of fullers and thoroughly closing the metal while at welding heat. This welding being very near the extremity of the work in progress, the small hole may become so flattened as not to be seen ; if so, the work is probably sound at the weld, and the hole may be again punched and drifted if necessary.

Another good weld is then given to the adjoining part intended for the arm, and the straight ends may then be made into part of a tongue-joint or scarf-joint.

By thus making the two bosses with half the lever to each boss, both pieces may be easily welded together while the thickness is rather greater than the required forged thickness; and, after being united, the lever can be lengthened to its desired length. A lever made by this method is shown by Fig. 158.

Another mode of making a small crank-lover is commenced by selecting a piece whose sectional area is about l1/2 times the mean sectional area of the lever arm required. One end of this piece is first tapered or curved on two opposite sides, and next upset, while at welding heat, by striking the work while in an upright position. This produces the desired shape for the outer extremity of the boss. The inner curved extremity or boundary of the boss, is next formed by top and bottom fullers while the work is between.