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 easiest to have some-
one watch the dial for you 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 you know you have reached the correct
When you are confident that you have adjust-
ed the inner spanner nut until zero spindle
end-play and preload exists, you now must
move the spanner inward and additional
0.001" to set the preload.
11. To set the preload, tighten the spanner nut an
additional 0.16" along its circumference. See
Figure 61 for the example of this measure-
Figure 61. Final spanner nut rotation.
12. Without causing the inner spanner nut to
tighten any further, install and 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, crack, or cause bearing failure.
13. Position the gasket correctly, and re-install
the outboard spindle cover.
To confirm that the bearings are correctly pre-
Make sure all safety precautions have been
taken and setup steps are complete to make
the lathe fully operational.
Install the chuck and tighten the jaws.
Set the spindle speed to its highest setting.
Connect the lathe to power and turn the lathe
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 pre-
load is too tight and you must repeat bear-
ing preload adjustment procedure..
G4003G Gunsmith's Lathe