TM 9-3419-234-14&P
(4) After making such an adjustment, open and close the
leadscrew nuts several times making certain the action is
smooth and the nuts do not bind.
Figure 8
(3) After removing, place the carriage on a bench in a
convenient working position as illustrated by Figure 7.
Remove the welsh plug m the top of the carriage and
Figure 9
loosen screws A and B , Figure 8, until the leadscrew
operating shaft can be withdrawn from the leadscrew jaw.
Loosen the retaining screw and withdraw the lower
leadscrew jaw shaft so the entire jaw assembly can be
removed. The leadscrew nut segments can now be
easily disengaged by removing three screws. Note that
each segment is positioned in the jaw by a locating pin.
(4) To replace the jaw assembly, it is necessary to
remove the leadscrew self oiling mechanism. Also, it
may be necessary to adjust the nut adjusting bushing to
eliminate excessive end play between the carriage and
Figure 10
the nut segments. See Leadscrew Nut Segments.
(5) After the carriage has been returned to the machine,
h. Carriage Vise Screws
the leadscrew nut lever will require adjustment to provide
(1) The vise screws employed in the carriage fronts or
the proper overtravel. To accomplish this, close the
vises of Threading Machines are adjustable for
leadscrew nuts on the leadscrew and loosen the lock nuts
eliminating end play.
on screws A and B as shown In Figure 8. Withdraw
(2) Excessive vise screw end play can result in the front
screw A several turns and tighten screw "B" until there is
being off-center, thus, the gripped workpiece will not be in
no overtravel or movement In the leadscrew lever. Then,
proper alignment when it is presented to the die head for
loosen screw B 1/6 of a turn and tighten screw A. Seat
threading.
Therefore, since the workpiece will not
the lock nuts on both screws to lock the adjustment.
correctly enter the chaser throats It is possible for
(6) If the leadscrew lever will not lock when the nuts are
closed on the leadscrew, loosen screw B and tighten
screw A until the lock will move into position. Then
proceed as described above to adjust the lever for
overtravel.
I. Leadscrew Nut Segments
(1) After extensive usage, the two leadscrew nut
segments may wear to permit excessive end play
between the carriage segments. This end play could
result in lead error.
(2) To adjust the leadscrew nut mechanism for end play,
remove the outboard leadscrew bearing and move the
carriage rearward until approximately one half of it
extends over the bed ways, Figure 9. Engage the
Figure 11
leadscrew nuts and loosen clamping screw B , Figure 10.
(Do not loosen screw A). Rotate the nut adjusting
bushing D, using a short pin.
(3) Correct adjustment allows .002" to .003" end play.
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