It is preferable, however, that the device for changing the direction of feed traverse be operative from the lathe carriage as in the Sellers lathe, so that the operator need not leave it when it is necessary to reverse the direction of traverse.
Fig. 571.
The swing frame, when the driving gear d is outside of the back bearing (as it is in [Fig. 570]), is swung from the axis of the lead screw as a centre of motion, and has two slots for receiving studs for change wheels. But when the driving gear is inside the back bearing as in [Fig. 571], the swing frame may be suspended from the spindle (r, [Fig. 565]) that passes through the lathe head, which may also carry the cone for the independent feed as shown in [Fig. 571], no matter on which side of the lathe the lead screw and feed rod are. This affords the convenience that when both lead screw and feed rod are in front of the lathe, the feed may be changed from the screw cutting to the rod feed, or vice versâ, by suitable mechanism in the apron, without requiring any change to be made in the driving gears.
Fig. 572.
![[Largeimage(143 kB).]](#8656825660018214284_large0186b.png.id-8768211424234326940.wrap-0.html.html){kind=link}