slide is securely bolted to the cross-feed nut that
A selective feed lever or knob for engaging the
moves back and forth when the cross-feed screw is
longitudinal feed or cross-feed as desired.
cross-feed handle is graduated to permit accurate
Half-nuts that engage and disengage the lead
infeed. Depending on the manufacturer of the lathe,
screw when the lathe is used to cut threads.
the dial may be graduated so that each division
They are opened or closed by a lever located on
represents a 1 to 1 or a 2 to 1 ratio. The compound
the right side of the apron. The half-nuts fit the
rest is mounted on top of the cross-feed slide.
thread of the lead screw, which turns in them
The carriage has T-slots or tapped holes for
like a bolt in a nut when they are clamped over
clamping work for boring or milling. When the lathe
it. The carriage is then moved by the thread of
is used in this manner, the carriage movement feeds
the lead screw instead of by the gears of the
the work to the cutting tool, which is revolved by the
apron feed mechanisms. (The half-nuts are
headstock spindle.
engaged only when the lathe is used to cut
You can lock the carriage in any position on the bed
threads, at which time the feed mechanism
by tightening the carriage clamp screw. Use the clamp
must be disengaged. An interlocking device
screw only when doing such work as facing or
that prevents the half-nuts and the feed
cutting-off, for which longitudinal feed is not required.
mechanism from engaging at the same time is
Normally, keep the carriage clamp in the released
usually provided as a safety feature.)
position. Always move the carriage by hand to be sure
it is free before you apply the automatic feed.
Aprons on lathes made by different manufacturers
APRON
differ somewhat in construction and in the location of
controlling levers and knobs. But, they all are designed
The apron is attached to the front of the carriage.
to perform the same functions. The principal difference
It contains the mechanism that controls the movement
is in the arrangement of the gear trains for driving the
of the carriage for longitudinal feed and thread cutting
and controls the lateral movement of the cross-slide.
automatic feeds. For example, in some aprons there are
You should thoroughly understand the construction
two separate gear trains with separate operating levers
and operation of the apron before you attempt to
for longitudinal feed and cross feed. In others, both
operate the lathe.
feeds are driven from the same driving gear on the feed
In general, a lathe apron contains the following
rod through a common clutch, with one feed at a time
mechanical parts:
connected to the drive by a selector lever. The apron
A longitudinal feed handwheel for moving the
carriage by hand along the bed. This
handwheel turns a pinion that meshes with a
rack gear secured to the lathe bed.
Gear trains driven by the feed rod. These gear
trains transmit power from the feed rod to
move the carriage along the ways and to move
the cross-slide across the ways, thus providing
powered longitudinal feed and cross-feed.
apron to engage or disengage the power-feed
mechanism. (Some lathes have a separate
clutch for longitudinal feed and cross-feed;
others have a single clutch for both.) (NOTE:
The power feeds are usually driven through a
excessive strain is put on the feed mechanism.
If clutches are not provided, there is some form
of safety device that operates to disconnect the
Figure 6-9.--Rear view of a lathe apron.
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