Fig. 675.
[Fig. 675] represents Hyde’s cutting-off machine, which consists of a hollow live spindle through which the bar of iron is passed and gripped by the chucks c c. At g is a gauge rod whose distance from the tool rest r determines the length of the work. f is a feed cone driven by a corresponding cone on the live spindle and driving the worm w, which actuates the self-acting tool feed, which is provided with an automatic motion, which throws the feed out of action when the work is cut off from the bar. The stand s is movable and is employed to support the ends of long or heavy bars.
To finish work smooth and more true than can be done with steel cutting tools in a lathe, what are known as grinding lathes are employed. These lathes are not intended to remove a mass of metal, but simply to reduce the surfaces to cylindrical truth, to true outline and to standard diameter, hence the work is usually first turned up in the common lathe to the required form and very nearly to the required diameter, and then passed to the grinding lathe to be finished. The grinding lathe affords the best means we have of producing true and smooth cylindrical parallel work, and in the case of hardened work the only means. In place of steel cutting tools an emery wheel, revolved at high speed from an independent drum or wide pulley, is employed, the direction of rotation of the emery wheel being opposite to that of the work.
Fig. 676.
[Fig. 676] represents Pratt and Whitney’s weighted grinding lathe. The headstock and tailstock are attached to the bed in the usual manner, the frame carrying the emery wheel is bolted to the slide rest as shown, the rest traversing by a feed spindle motion. The carriage traverse is self-acting and has three changes of feed, by means of the feed cones shown.
To enable the lathe to grind taper work (whether internal or external) the lathe is fitted with the Slate taper attachment shown in [Figs. 508] and [509].
It is obvious that in a lathe of this kind, there must be an extra overhead shaft, driving a drum of a length equal to the full traverse of the lathe carriage, or of the plate carrying the head and tailstocks, and the arrangement of this drum with its belt connection to the pulley on the emery wheel arbor, is sufficiently shown in [figure]. To protect the ways of the bed from the abrasion that would be caused by the emery and water falling upon them, guards are attached to the carriage extending for some distance over the raised Vs.