In every shop where steam engines are manufactured the smith is called upon to forge the connecting rods. These are of great variety in size as well as in the shape of the stub ends. They are preferably forged of a single piece; but may be made from two or three. When of two pieces, the stub ends and one-half the rod are made in one piece with the weld in the center. When of three pieces each stub end and center of the rod is forged separately and then welded together. The form of the stub ends varies with the method used in fastening the brasses in position.
In order to forge a connecting rod of moderate dimensions, proceed as follows: Let us consider a rod having flat stub ends suited for brasses fitted with straps and keys. A block is first hammered down to a sectional area approximating that of the stub ends. It is then fullered out at H H (Fig. 80). After this has been done the central portion of the rod is drawn out to the diameter and length desired. The finished forging is shown in Fig. 81. Special care is required in the calculation of the weight of the rod's central portion : Also in the determination of weight for the corresponding section of the block and the proper location of the fuller marks H H. Unless these are properly located the proper weight or length of the rod center will not be obtained.