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11. Insert chuck key into a cam socket to prevent
spindle from turning, then tighten inner span-
ner nut until dial indicator needle just stops
moving (see Figure 158).
Figure 158. Adjusting spindle bearings.
Note: For convenience and accuracy, we
recommend having another person watch the
dial while you tighten the inner spanner nut.
While tightening the inner spanner nut,
rock the spindle back and forth slightly with
the chuck key to make sure the spindle
tapered roller bearings seat properly in their
races.
When the dial indicator needle stops mov-
ing, there will be no spindle end-play and no
bearing preload. It is important that you find
this point without tightening the spanner nut
too much and inadvertently preloading the
spindle bearings.
If you think you have gone past the zero end-
play point, unload the bearings by repeating
Steps 7–8, then retighten the inner spanner
nut until it has reached the zero end play
position.
Model G0791 (Mfd. Since 9/15)
12. Tighten spanner nut an additional
its circumference. See Figure 159 for exam-
ple of this measurement.
Figure 159. Final spanner nut rotation.
13. Without allowing inner spanner nut to tighten
any further, install and tighten outer spanner
nut against the inner nut.
Do not overtighten outer spanner nut because
additional preload can force bearings even
tighter against races in headstock and cause
headstock to compress, or crack, or cause
bearing failure.
Confirming Bearing Preload
1.
Re-attach removed lathe components and
prepare it for operation.
2.
Install chuck and tighten jaws.
3.
Set spindle speed to highest setting.
4.
Connect lathe to power and lathe spindle ON.
5.
Let lathe run for 20 minutes, periodically shut-
ting it down a few times and checking spindle
nose temperature (refer to next step).
6.
Turn spindle OFF, disconnect lathe from
power, and check temperature of spindle.
—If spindle nose is slightly warm to touch,
you have correct bearing preload.
—If spindle nose is too hot to touch, preload
is too tight and you must repeat bear-
ing preload adjustment procedure. When
repeating procedure, rotate inner spanner
nut a little less during Step 12 in preceding
instructions.
⁄
" along
1
16
⁄
" Travel
1
16
-93-
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