Bent Spindle?

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DeanB

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I have a 40's vintage V54 that I bought as part of a package from someone that bought it from the original owner. The person I had it from never ran it.
Now I know why. With a known straight and uniform bar in the chuck there is ~ 0.012 runout at 8" from the chuck. Does it with 2 different chucks. The high spot is always the high spot. In other words the 12 thousandths moves as I rotate and is always the same clock location on both chucks. When I indicate the outside of the spindle it's less than 0.0005 runout. The face of the spindle is maybe 0.0015 runout. Feels almost like the spindle is bent?
Looking for ideas how to correct this.
Thanks,
Dean
 
Have you put an indicator on the inside taper of the spindle? That would be the definitive test for a bent spindle.
That, and measuring the face of the shoulder (the hub that the chuck runs up to and stops)
It's possible that both chucks were not mounted correctly and the spindle is fine- if that is true then it should be possible
to skim the chuck backplates (if they have backplates and are not one-piece chucks) and correct some/most of the error
It's also possible that the spindle threads have been damaged in some way or have burrs- inspect closely

-M
 
Last edited:
I have checked the face of the shoulder. Approximately 0.0015 runout on that face. Threads are clean but I should look for any damage or burrs.

Thanks
 
Are your chucks backplate type or one piece?
Also, remember that 3 jaw standard chucks are expected to have some error- 0.003" is typical so 0.012" at 8" might not be too unusual
especially if they are worn
 
How worn are the chuck jaws. Often times older chucks have one or more jaw that's bell mouthed. About the best "known straight and uniform bar" would be a dowel pin. I have several different lengths and sizes of 4140 alloy from McMaster for this very purpose. The largest I use is 1" in diameter and 10" long. It's guaranteed to have less than .0003" runout. I like the fact that dowel pins are hardened. It's unlikely you'll bend, mar or break one.
 
Not saying it couldn't be bent- it's possible. You just want to check all the other possibilities just in case it's something easier to fix
 
markba633csi said:
Are your chucks backplate type or one piece?
Also, remember that 3 jaw standard chucks are expected to have some error- 0.003" is typical so 0.012" at 8" might not be too unusual
especially if they are worn
Click to expand...
One of each. The original ATLAS is one piece, a newer Shars has a backplate. Both exhibit the same runout at an equal distance from the spindle.
 
markba633csi said:
Not saying it couldn't be bent- it's possible. You just want to check all the other possibilities just in case it's something easier to fix
Click to expand...
That's what I've been working through to find all the easily fixable things first. Striking out so far.
 
Is your lathe leveled with no bed twist? Headstock out of alignment?
Do you have excess play in the spindle? If you have Babbitt bearings it might be as simple as getting some slop removed by removing a bit of shims.


Cutting oil is my blood.
 
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