insert the chuck wrench into a cam socket to
prevent the spindle from turning, then tighten
the inner spanner nut until the dial indicator
needle just stops moving (see figure 112).
While tightening the spanner nuts, rock the
spindle back and forth slightly with the cam
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 zero spindle end-play and
no bearing preload. it is essential that you
find this point without tightening the spanner
nut too much and inadvertently pre-load the
figure 112. Adjusting spindle bearings.
since it takes 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. it is easiest to have someone watch the
dial while you tighten the inner spanner nut.
if you think you may have gone past the zero
end-play point, take the time to unload the
bearings as described earlier, then re-tighten
the inner spanner nut until it has reached the
zero end play position.
10. tighten the spanner nut an additional
Model G0709 (Mfg. Since 5/11)
11. Without allowing the inner spanner nut, to
tighten any farther, tighten the outer spanner
nut against the inner nut.
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 the bearing may quickly
To confirm that the bearings are correctly pre-
re-attach all removed lathe components and
prepare it for operation.
install the chuck and tighten the jaws.
set the spindle speed to its highest setting.
Connect the lathe to power and turn the lathe
periodically shutting down the lathe a few
times and checking temperature, let the lathe
run for 20 minutes.
turn the spindle OFF, disconnect lathe from
power, and check the temperature of the
—if the spindle nose is slightly warm to the
touch, you have correct bearing preload.
—if the spindle nose is hotter than you
can comfortably keep your hand on, the
preload is too tight and you must repeat
the bearing preload adjustment procedure.
When repeating the procedure, rotate the
inner spanner nut a little less during Step
10 in the preceding instructions.