Fig. 1269.
In [Fig. 1268] is a plan view of the chuck, work, and lathe rest; d is a former attachment bolted to the slider of the rest, and e a rod passing through the lathe block. The weight w, [Fig. 1269], is suspended by a cord attached to the slide rest so as to keep the former d firmly against the end of e.
As the slider is operated, the rest is caused by e to slide upon the lathe bed, and the cutting tool forms a spherical curve corresponding to the curve on the former d. The weight w of course lifts or falls according to the direction of motion of the slider.
The cut is put on by operating handle g, thus causing e to advance.
The weight w causes any play between the slider and the cross slide to be taken up in the same direction as the tool pressure would take it up, hence the cut taken is a very smooth one. The half-round mandrel being fixed to the lathe face plate will remain true, obviating the liability of the centre of the spherical surface being out of line with the axis of the bearing-bore.
Fig. 1270.