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Power downfeed takeoff
The worm gear, right, is item #26 in the components diagram.
Quill and quill locks are to the right of the DRO.
gears, 33 in Headstock-2.
5. When power downfeed is ON, spindle power drives
worm 26, which in turn drives handwheel 59, shaft 46
and worm 6, which rotates continuously CCW, as seen
looking left from the downfeed lever end.
6. In the Power-ON mode, the quill can still be operated
drill-press style, but this is not recommended. Be sure
that levers 3 are pivoted fully inward, and are held that
way by tightening lever stop screw 45.
Power downfeed action
7. In the Power-ON mode, levers 3 are pivoted out-
ward to engage the clutch, see note (6). The quill is now
driven downward by shaft 46 and worm gear 6. Down-
ward motion stops when the clutch is disengaged by pin
7 contacting pin 5; this occurs when the zero-depth line
on collar 3 coincides with the scale datum. Ramping of
7 on 5 pushes the clutch actuator to the right, allowing
spring action (9) to snap dogs 7 away from the inner
ratchet of 6. At this point the quill is free to return to its
starting position.
8. When power downfeed is activated, the left-hand-
threaded hub 9 unscrews out of the tabbed nut 0,
which is located in a pocket in the gearbox casting. This
drives 0 to the right, but has no other effect provided
PM-940M 0-206 v.indd
the clutch is released at the zero-depth line by pins 5
and 7, note (7).
9. Ordinarily, the depth collar will be zeroed at a point
where the quill is well within its normal range of motion.
On the other hand, if the depth collar is zeroed with the
quill at near full travel, there is the possibility that the ac-
tion of pins 5-7 may not occur even if the quill is close to
bottoming out on the dog screw, see "Quill travel".
0. To preempt this potential problem, tabbed nut 0 pro-
vides a backup release mechanism. It does this — in
the process of unscrewing itself from hub 9 — by push-
ing against the shoulder on actuator 4. This has exactly
the same effect as a routine release via pins 5 and 7.
Rate selection
. Gears 49, 50 and 5 are keyed as one block to the
output shaft, 46. All three are permanently meshed
with their opposite numbers 3, 30 and 29 on power in-
put shaft 20. Full-time meshing like this is possible be-
cause only one of the gears 29-30-3 is keyed to 20 at
any given time, thus transmitting power at the selected
rate. The other two gears free-wheel.
2. A pinion on feed rate selector shaft 37 controls the
position of shaft 22, the inner end of which slides within
34
Power downfeed gear assembly
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