MIL-L-23249D
for lathe centers, faceplates and chucks. The inner and outer surfaces of
the spindle nose on which work holding devices are mounted shall be hardened
to prevent wear.
3.4.5 Spindle drive. The lathe shall have a spindle drive mechanism that
will provide the required range of spindle speeds listed in table I. The
spindle shall be driven through an all gear or combination gear and belt
drive by an electric motor as specified in table I. All gears shall meet
the requirements of 3.3.9.
3.4.6 Spindle speed change mechanism. The spindle speed mechanism shall
be the manual speed change, the manual speed change with pre-select power
shift or the variable speed type. The shifting mechanism shall be designed
so that speed change cannot occur unintentionally. Except for the variable
speed drive, speeds shall be in geometric progression within 10%. The
manual speed change mechanism shall allow spindle speed changes by
positioning gear shift levers or dials located on the front side of the
headstock. Speeds shall be selected by positioning the levers as indicated
on a conveniently located speed chart or by positioning a direct reading
dial. The manual speed change with pre-select power shift shall provide
spindle speed selections by manually-setting a selector control to the
desired spindle speed. It shall be possible to pre-select the next spindle
speed while still cutting, then automatically initiate the shift upon
activation of the spindle control. The variable speed change mechanism
shall permit spindle speed adjustments to compensate for varying machine
conditions. Optimum speeds shall be obtained by gear range selection and by
variable speed adjustment within the range. It shall be possible to adjust
speed within a gear range while running. The actual spindle speed in RPM
shall be shown by a speed indicating device located convenient to the
operator.
3.4.7 Feed-thread gearbox. The lathe shall have a feed-thread gearbox
which changes the ratio of the speed of the spindle with respect to the lead
screw and feed rod to obtain the-feed rate and thread lead required. Unless
otherwise specified (see 6.2.1), the lathe shall be capable of producing
inch and metric threads over the thread ranges specified in table I. The
feeds shall be by a geared feed mechanism providing both manual and power
operation. Power to the feed mechanism shall be through a separate feed rod
and lead screw. A safety clutch or similar device shall protect the feed
mechanism from damage by overload or jamming. It shall be possible to feed
and thread in either direction independently of the direction of spindle
rotation and to provide a means to reverse the leadscrew when cutting metric
threads. A feed and thread chart shall be mounted near the gearbox as a
ready reference for feed and thread selections. All feed and thread
selections shall be shown without need for mathematical conversion. When
specified (see 6.2.1), a combination inch/metric gearbox shall be
furnished.
3.4.8 Carriage. The lathe shall have a carriage that supports the apron,
cross slide, compound rest, and other related equipment. The carriage shall
traverse longitudinally on the bed ways. The carriage shall be fitted to
the bed ways and shall have means of compensating for wear between sliding
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