On the inclined shaft is a worm, or, as the makers term it, a spiral pinion of several teeth which gears into a straight toothed spur gear-wheel, giving a smooth and rolling tooth contact, and therefore producing an even and uniform feed motion.
This spur gear is fast on a shaft c, which is capable of end motion and is provided on each of its side faces with an annular toothed clutch. On each side of this spur-wheel is a clutch, one of which connects with the train of gears for the turning feed, and the other with the cross-feed gear b.
When the shaft (whose end is shown at c, and to which the spur gear referred to is fast) is pulled endways outwards from the lathe bed, its front annular clutch engages with the clutch that sets the cross-feed gear b in motion, and b engages with a pinion which forms the nut of the cross-feed screw.
When shaft c is moved endways inwards its other annular clutch engages the clutch on that side of it, and the turning feed is put into operation. The method of operating shaft c endways is as follows:—
In a horizontal bearing d is a shaft at whose end is a weighted lever l, and on the end of this shaft is a crank pin shown engaging a sleeve e which affords journal bearing to the outer end of shaft c, so that operating the weighted lever l operates e, and therefore shaft c with the spur gear receiving motion from the worm. A simple catch confines lever l to either of its required limits of motion, and allows the free motion of the operating lever to start or stop either the longitudinal or the cross feed, either of which is started or stopped by this lever, but no mistake can occur as to which feed is operated, because the catch above mentioned requires to be shifted to permit the feed to be operated.
The lower end of the bell crank f engages with the sleeve e, so that when the shaft c is operated outwards the horizontal arm of bell crank f is depressed and the spur pinion of the cross-feed nut is free to revolve, being driven by the cross-feed motion. When the lever f is moved towards the lathe bed (which occurs when the stop or catch is set to allow the longitudinal feed to be used) the nut of the cross feed is locked fast by the horizontal arm of the bell crank f. This device makes the whole action from one direction of feed to another automatic, and the attention of the workman is not needed for any complicated adjustment of parts preparatory to a change from one feed to the other.
At h is a hand wheel for hand feeding, the pinion r meshing into the rack that extends along the front of the lathe bed; back of the hand wheel and at h′ a clamp is provided whereby the saddle or carriage may be locked to the lathe bed when the cross feed is being used, thus obviating the use of a separate clamp on the bed.
The top slide of the compound rest is long and its guideway is short, the nut being in the stationary piece g, and it will be observed that by this arrangement at no time does the bearing surfaces of the slides become exposed to the action of chips or dirt.
