When the feed selection lever and carriage lock
are disengaged, the half-nut lever (figure 59)
can be moved downward from the disengaged
upper position to clamp the half nut around the
leadscrew for threading operations.
figure 59. half nut lever.
DO NOT engage the half nut if the leadscrew
will rotate over 200 RpM, or if the carriage
lock is applied. Disregarding this warning
may cause damage to the bearings or the
leadscrew shear pin to break.
When cutting inch threads and the pass has been
completed, the thread dial (see figure 60) allows
the machinist to disengage the carriage from the
leadscrew, and quickly return the carriage for the
next pass. Based on the thread tpi being cut, and
what is indicated on the thread chart, the dial indi-
cates where the machinist must re-clamp the half
nut in order to resume the same thread to avoid
When cutting metric and other types of threads, the
thread dial must be disengaged from the leadscrew,
and the half nut clamped to the leadscrew until the
threads are complete. otherwise the path of the
same thread will be lost. All carriage returns for
non-inch threads are made by backing the tool
point out of the thread, and reversing spindle rota-
tion with the spindle on/oFF lever.
to engage the thread dial, loosen the mounting
cap screw, then pivot the dial into the leadscrew
so the gear teeth mesh with the leadscrew.
retighten the cap screw to hold the thread dial in
Model G0709 (Mfg. Since 5/11)
the thread dial chart is located on the headstock
cover, as shown in figure 60 and 61.
figure 60. thread dial chart and thread dial
figure 61. thread dial chart.