Bad spindle?

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spartan2381

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I have a G0776 lathe and have been experiencing a large degree of runout and vibration on the spindle. When a chuck is attached it wobbles to such a degree that I have excess vibrations and can’t make any accurate cuts. I’m wondering what could be causing this. I have taken some videos to help show the issue. Could it be a bent spindle, bearing, etc?

Spindle without chuck
Spindle with chuck
 
Belt was a little loose, tightened which help with some of the vibration but still have wobble in the chuck, especially when using the Set-Tru Gator Chuck.

IMG_1864.jpeg
 
What is the best way to check for bearing pre-load? I don't notice an in-out play when pushing/pulling on spider.
 
Plus 1 for bearing preload.
Check your nuts on the outboard end
How tight is the chuck fitted?
Is it screwed on or cam lock?
Loose belts don't make for wobbly chucks.
Loose nuts do.
 
Spindles are very robust. It is difficult to permanently “bend” a spindle, without making it obvious. An event that bent the spindle would likely damage other components.
 
You would need to use a dial type indicator to pinpoint the problem
Camlock type spindles need to be clean- no chips
Is this a new lathe? Has it always been like this?
-Mark
 
on a South Bend you put a bar down the spindle and a dial indicator (or DTI) on the top of the spindle. Push down with the bar and zero the DI, then pull up with some reasonable strength and note the movement of the DI needle. The aim for an SB is a bit less than 0.001". Not entirely sure what it would be for a gear head lathe, probably a bit less. On an SB, preload is adjusted two ways - radial by adding or removing shims, axial by tightening the end nut at the other end of the spindle. On a gear head lathe, I think it's just a two piece jam nut.

Another couple of ways of testing preload. Put a chuck on the spindle and remove the belt tension. Give it a sharp spin - the chuck should rotate no more than one full revolution. Also you can go by temperature - the bearings should warm up enough to feel after a 20 or 30 minute run if the preload is set right. No warm up = too loose. Hot enough to boil water = too tight.
 
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