Grizzly G9249 - Manual (Page 62)

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g9249 12" x 37" Belt drive gap Bed lathe
9. Move the carriage toward the spindle an
additional 0.100".
10. tighten the inner spanner nut until you see
the motion of the dial indicator needle just
barely stop moving. during the spanner nut
tightening process, rock the spindle back and
forth slightly to make sure the spindle bear-
ings seat properly in the races.
Note: When the dial indicator needle stops
moving, there will be no spindle end-play and
no bearing preload. It is essential that you
find this exact point without tightening the
inner spanner nut too much and inadvertently
preload the spindle bearings.
Since it can take great effort to turn the inner
spanner nut, you may find it difficult to know
if you have gone past the zero end-play
point or not. You may find it easier to have
an assistant watch the dial for you while you
tighten the spanner nut. If you think you may
have gone past the zero end-play point, take
the time to unload the bearings as described
in earlier steps, then re-tighten the spanner
nut until you know you have reached the cor-
rect setting.
11. to set the correct amount of spindle bear-
ing preload, rotate the inner spindle lock nut
clockwise an additional 0.13" along its cir-
cumference. see
figure 105 for an example
of this measurement.
figure 105. example of final inner spanner nut
travel.
0.13" travel
12. Without causing the inner spanner nut to
tighten any further, install and tighten the
outer spanner nut against the inner nut.
Note: Do not overtighten the outer spanner
nut because additional preload can force the
bearings even tighter against the races in the
headstock and cause the headstock to com-
press or crack, or cause bearing failure.
13. re-install the change gear door.
To confirm that the bearings are correctly pre-
loaded:
1. Make sure all safety precautions have been
taken and setup steps are complete to make
the lathe fully operational.
2. remove all tools and materials used during
the bearing preload process.
3. set the spindle speed to its highest setting.
4. Connect the lathe to power and turn it ON.
5. let the lathe run for 20 minutes.
6. turn the spindle OFF, disconnect the lathe
from power, and check the temperature of the
spindle.
— if the inboard end of the spindle tube is
slightly warm to the touch, you have the
correct bearing preload.
— if the inboard end of the spindle tube is
hotter than you can comfortably keep your
hand on, the preload is too tight and you
must repeat the spindle bearing preload
adjustment procedure.