Fig. 3070.
Fig. 3071.
[Figs. 3070] and [3071] represent a machine for forging threads on rods and screws. As forgings, the threads are beautifully clean, and for the general work of coach screws much stronger than the cut threads. A perspective view of the machine is given in [Fig. 3070], and a vertical of it shown in [Fig. 3071]. In the former figure, a b are the screw dies. The rod or bolt to be threaded is placed upon the lower die b, and fed forward while screwing it. The upper die is mounted on a slide c, which is actuated in the downward direction by an eccentric e on the main shaft and the toggle-bar d, the upward motion being obtained by an internal spiral spring f. The lower die b is carried in a slide g, and is adjusted at the proper distance from the upper die by means of wedge h, and the inclined plate i, beneath the slide g. The wedge h is operated by a pedal l, and secured in its highest position by a bolt j, received in a mortice made in the plate i, the bolt being operated by a pedal m. In order to release the wedge and return it to its lowest position, the bolt is raised by pressing down the pedal m, whereby the wedge is free to be returned by the counterweights k, in connection with pedal l; slide g, carrying the lower die, then descends by its own gravity, and so separates the two dies sufficiently to allow of the removal of the screw-bolt or rod therefrom. To compensate for the wear of the dies, and admit of their adjustment, another wedge o, with screw adjustment, is disposed below the inclined plate i.
Fig. 3072.
[Fig. 3072] represents a lag screw forged by the machine.