# Gs0768 Bearing Loading



## catoctin (Sep 21, 2016)

I picked up a new G0768 early in the summer and hit a issue while checking out the run out on a new chuck.  My new chuck is a 5" model from LMS.  I am using a 3" piece of 3/8" piece of carbide rod as a checking sample.  My indicator is rigidly mounted on the tool post.  My measurements are being taken about 1/2" from the chuck.  Rotating the chuck mount location around, I got the measured run out <.0005".  This is fine.  The thing I noted is that I can deflect the reading about .001" by pressing on the chuck.  Is this normal?


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## catoctin (Sep 24, 2016)

Has anyone attempted a spindle bearing replacement on this lathe?  It appears they use generic 30206 tapered roller bearings.


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## mksj (Sep 24, 2016)

I would say that it is normal for this size/type of machine.  You could try to check the bearing preload first as opposed to replacing the bearings. It is a very unusual to see the spindle bearings go. There are also different grade ratings for bearings, so although it may be a standard bearing, the quality/brand of bearing can be a major factor.


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## catoctin (Sep 25, 2016)

mksj said:


> I would say that it is normal for this size/type of machine.  You could try to check the bearing preload first as opposed to replacing the bearings. It is a very unusual to see the spindle bearings go. There are also different grade ratings for bearings, so although it may be a standard bearing, the quality/brand of bearing can be a major factor.


I am curious if simply torquing the main bearing nut is enough to increase the preload.  The manual was of little help since it had no reference to the preload.  I believe the parts diagram for the lathe maybe incorrect in terms of the stacking on the bearings, grease seals, and casting seals.  The grease seals are depicted as last in on the chuck side of the spindle and first in on the pulley side.  

I know there are various grades of bearings for a particular part number.  Is there a good online source for the better bearings?  I see 30206J only for NSK online.


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## rongross (Nov 10, 2019)

I have the G0768 (new) and my problem is that I feel roughness in turning the spindle that goes away when I release the pre-load but then there is visible space between the spanner nuts.  I worry that my bearings were loaded too much at the factory and were damaged. I also cannot inspect them or lubricate them because there is no lubrication ports.

Have your problems been corrected?  Any thought would be greatly appreciated.


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## Mitch Alsup (Nov 10, 2019)




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