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Copyright © 2020 Quality Machine Tools, LLC
PM-1440GT v9 2020-10
Figure 3-12
Feed control levers on the apron
The split nut lever is used only for thread cutting. In the main photo the
power feed lever is in its neutral — disengaged — state. To power the
saddle (
Longi
), pull the lever OUT and UP, inset. To power the cross-
slide, push the lever IN and DOWN. Test for engagement/dis-engage-
ment by gently jiggling the saddle and cross-slide handwheels.
Gear
shifters
I - W
I - X
I - Y
I - Z
Saddle Cross-
slide
Saddle Cross-
slide
Saddle Cross-
slide
Saddle Cross-
slide
A - D
0.021
0.0105 0.0295
0.0148 0.0368 0.0184
0.0226 0.0113
B - D
0.0105 0.0053
0.0148
0.0074
0.0184
0.0092 0.0113 0.0057
A - C
0.0053 0.0027 0.0072 0.0036 0.0092 0.0046 0.0056
0.0028
B - C
0.0026 0.0013 0.0036
0.0018
0.0046 0.0023
0.0028
0.0014
Figure 3-14 lists inches of travel per revolu-
tion of the spindle, rounded to the nearest
0.001". Saddle motion is 2 times cross-slide
motion. In practice most users stay with only
the one gear shift setting, such as I-X, con-
trolling the feed rate by the "doubler knobs",
A-B and C-D. For an overall faster feed rate,
use I-Y.
SADDLE & CROSS-SLIDE FEED RATES
Use the same change gear setup as for TPI thread cutting
(30T upper/60T lower, following page
Figure 3-14
Power feed rates (inches per spindle rev)
FEEDSHAFT CLUTCH
The clutch shown in Figure 3-15 disengages the power feed if
the saddle or cross-slide hits an obstruction when power feed-
ing, thus minimizing the potential for damage. This could be
the result of either an accidental event, or deliberately stopping
the saddle at a precise location set by the stop, Figure 3-13.
The clutch comprises a pair of spring loaded steel balls bear-
ing on a detent disc driven by the saddle feed gearbox. Spring
pressure is adjusted by two set screws on either side of the
feed shaft, arrowed in Figure 3-15. Setting the spring pres-
sure is a process of aiming for the best compromise between
too high — damaging feed pressure — and too low, stopping
prematurely.
Setting the clutch to work reliably with the micrometer carriage
stop is a good example of such a compromise: start with low
spring force, then work up in small increments until the car-
riage stops in the same location (say ± 0.002”, assuming a
constant depth of cut and feed rate).
SADDLE STOP
The stop assembly, Figure 3-13, has a micrometer-style collar
graduated in 0.001 in. divisions. It can be clamped at any point
along the lathe bed (two M6 socket head screws on the under
-
side secure the clamp plate to the block). Make certain that the
stop rod seats firmly on the saddle casting.
Figure 3-15
Feedshaft clutch
Figure 3-13
Saddle stop
