Paul Weber wrote:

The runout is the same on the inside taper, over .002.
So much for buying old American iron.


Well, you can pull it apart and check for any obvious signs
of improper repairs, damaged parts, etc. Check the bearings to make
sure they are not damaged (it may not take a badly dented roller or inner
race to produce the symptoms you describe. When you get the spindle
out, you can try rolling it on a surface plate to look for actual bending.
If the bending is obvious, you can check around to see who can make
a new spindle for you. A very servicable spindle is not that hard to make,
especially if you can get access to a toolpost grinder. Make a spindle
"blank", in other words, don't finish the inside taper or the chuck mounting
threads until the spindle is back in YOUR lathe headstock. You can cut
the inside taper with the compound slide. You use a known-good male
taper as a master, and use blue dye to check the fit. When you get even
marking of the blue dye, the angle of the compound is exactly right, then
grind a little at a time until the arbor goes to the correct depth.

Cutting the taper for the chuck is easier, and you just test fit the chuck
until it threads on smoothly.

If the bend in the spindle is only at the outer tip, you can just reface the
backplates of all your chucks, and regrind the inside taper until it
runs true.

Jon