r slide, as
shown, and it can be moved with relation to the work by the movement of
the carriage _C_ along the bed, or by moving slide _D_ crosswise. The
lengthwise movement is used to feed the tool along the work when
turning, boring or cutting a screw, and the crosswise movement for
facing the ends of shafts, etc., or for radial turning. When the tool is
to be fed at an angle, other than at right angles to the bed, slide _E_,
which can be set to the required angle, is used. The lengthwise and
crosswise feeding movements can be effected by power, the lengthwise
feed being engaged by tightening knob _k_, and the cross-feed by
tightening knob _l_. The direction of either of these movements can also
be reversed by shifting lever _r_. Ordinarily the carriage and slide are
adjusted by hand to bring the tool into the proper position for turning
to the required diameter, and then the power feed (operating in the
desired direction) is engaged. The tailstock _T_ can be clamped in
different positions along the bed, to suit the length of the work, and
its center _h_{1}_ can be moved in or out for a short distance, when
adjusting it to the work, by turning handle _n_.

[Illustration: Fig. 2. Plan View of Lathe Headstock showing Back-gears]

[Illustration: Fig. 3. Feed Mechanism of Lathe Apron]

As some metals are much harder than others, and as the diameters of
parts to be turned also vary considerably, speed changes are necessary,
because if the speed is excessive, the turning tool will become dull in
too short a time. These speed changes (with a belt-driven lathe) are
obtained by placing the driving belt on different steps of cone-pulley
_P_, and also by the use of back-gears. The cone-pulley can be connected
directly with the spindle or be disengaged from it by means of bolt _m_.
When the pulley and spindle are connected, five speeds (with this
particular lathe) are obtained by simply shifting the driving belt to
different steps of the cone. When a slower speed is required than can be
obtained with the belt on the largest step of the cone, the latter is
disconnected from the spindle, and the back-gears _G_ and _G_{1}_ (shown
in the plan view Fig. 2) are moved forward into mesh by turning handle
_O_; the drive is then from cone-pulley _P_ and gear _L_ to gear _G_,
and from gear _G_{1}_ to the large gear _J_ on the spindle. When driving
through the back-gears, five more speed changes are obtained by shifting
the position of the