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Copyright © 2021 Quality Machine Tools, LLC
PM-1340GT v8 2021-04
gives spindle speeds from 90 to 475, high speed from
335 to 1800 rpm. Because many users find that one
range or the other is suitable for most of their work, there
is typically little need to swap belts. If the drive needs
to be reconfigured, loosen the lever securing the motor
platform to the slotted stay, Figure 3-3. Raise the motor
to de-tension, reposition the Vee belt, then lower the mo-
tor to re-tension — not fully weight bearing, just enough
to drive reliably without slipping. Re-tighten the lever.
SPINDLE SPEEDS
The PM-1340GT has a six-speed headstock gearbox
with two shift levers
L-H
and
1-2-3
, Figures 3-1 and
3-4. Before changing speed,
STOP THE MOTOR
,
Figure 3-2, then move each shift lever to the desired
setting. This calls for care and patience because it
is not always possible to go directly from one mesh
to another. Move the spindle back and forth by hand
while easing the lever into its detent (meshed) position.
Don’t use the JOG button in this process
— this
may cause gear damage.
CARRIAGE FEED DIRECTION
The black knob below
the speed selection levers on the
front panel, Figure 3-1, determines whether the power
feed is right to left — the usual direction for turning and
thread cutting — or reversed. The selected direction ap-
plies to both the leadscrew and the carriage/cross slide
power feed.
Before changing feed direction,
STOP THE MOTOR
.
Hand-turn (jiggle) the spindle while feeling for the mesh,
as above.
CARRIAGE FEED GEARBOX
The carriage feed gearbox (a.k.a. quick-change gear
-
box) has two separate outputs: 1. An 8 TPI leadscrew,
used primarily for thread cutting, linked to the carriage
by a split nut in the apron, and; 2. A keyed power-feed
shaft driving a worm, in the apron, which in turn drives
either the carriage or the cross slide.
SPINDLE SPEED (RPM)
1
2
3
H
1800
770
1160
L
475
205
308
H
780
335
505
L
205
90
135
Headstock Vee
belt pulley
Figure 3-4
Vee belt configurations
High
range
Low
range
For all TPI standard
threads (U.S.A.) the
127T gear is simply
an idler between up-
per and lower gears.
Figure 3-6
Standard TPI setup
Figure 3-5
External change gears
The carriage feed gearbox is driven by external change
gears, Figure 3-5.
For all standard U.S. thread cutting (TPI) the exter-
nal gears are always 40T upper, 40T lower
— see Fig-
ure 3-6. For these non-metric operations the power-feed
rate relative to spindle speed is entirely controlled by the
two gear shift levers below the main control panel, Fig-
ure 3-1. Note also that the 40T-40T setup delivers the
feed rates shown in the thread chart, Figure 3-7.
The knob with pointer, right of the thread chart, selects
the gearbox output — carriage feed shaft (left, counter
