driving belt, as before. The fastest speed with the
back-gears in mesh is somewhat slower than the slowest speed when
driving direct or with the back-gears out of mesh; hence, with this
particular lathe, a series of ten gradually increasing speeds is
obtained. Changes of feed for the turning tool are also required, and
these are obtained by shifting the belt operating on pulleys _p_ and
_p_{1}_ to different-sized steps. On some lathes these feed changes are
obtained through gears which can be shifted to give different ratios.
Many lathes also have gears in the headstock for changing the speeds.

[Illustration: Fig. 4. Rear View of Lathe Apron]

Front and rear views of the carriage apron, which contains the feeding
mechanism, are shown in Figs. 3 and 4, to indicate how the feeds are
engaged and reversed. The feed-rod _R_ (Fig. 1) drives the small bevel
gears _A_ and _A_{1}_ (Figs. 3 and 4), which are mounted on a slide _S_
that can be moved by lever _r_ to bring either bevel gear into mesh with
gear _B_. Gear _B_ is attached to pinion _b_ (see Fig. 3) meshing with
gear _C_, which, when knob _k_ (Fig. 1) is tightened, is locked by a
friction clutch to pinion _c_. The latter pinion drives gear _D_ which
rotates shaft _E_. A pinion cut on the end of shaft _E_ engages rack _K_
(Fig. 1) attached to the bed, so that the rotation of _E_ (which is
controlled by knob _k_) moves the carriage along the bed. To reverse the
direction of the movement, it is only necessary to throw gear _A_ into
mesh and gear _A_{1}_ out, or _vice versa_, by operating lever _r_. When
the carriage is traversed by hand, shaft _E_ and gear _D_ are rotated by
pinion _d_{1}_ connected with handle _d_ (Fig. 1).

The drive for the cross-feed is from gear _C_ to gear _F_ which can be
engaged through a friction clutch (operated by knob _l_, Fig. 1) with
gear _G_ meshing with a pinion _H_. The latter rotates the cross-feed
screw, which passes through a nut attached to slide _D_ (Fig. 1), thus
moving the latter at right angles to the ways of the bed. The cross-feed
is also reversed by means of lever _r_. As previously explained,
lead-screw _S_ is only used for feeding the carriage when cutting
threads. The carriage is engaged with this screw by means of two
half-nuts _N_ (Fig. 4) that are free to slide vertically and are closed
around the screw by operating lever _u_. These half-nuts can only be
closed when lever _r_ is in a central or neutral position, so that