I would have to say your problem lies in the spindle bearings. Whether or not it can be fixed by adjustment remains to be seen. I had a very similar problem on my Enco 9x12. In my case the problem was present as soon as I bought it.
I suggest you try this. Put a pice of drill rod or similar in a colett or 4-jaw chuck and then see how closely an indicator reads when rotating the spindle. In my case it was impossible to get it dead nuts because a high reading showed up on every second revolution no matter what I did. A sure sign of a bad bearing. Adjustment did nothing. I replaced the bearings and the problem disappeared . I don't know exactly what the problem was with a bearing but the rotation of a bearing will bring any given ball or roller around to the same spot on 2 revolutions.
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I suggest you try this. Put a pice of drill rod or similar in a colett or 4-jaw chuck and then see how closely an indicator reads when rotating the spindle. In my case it was impossible to get it dead nuts because a high reading showed up on every second revolution no matter what I did. A sure sign of a bad bearing. Adjustment did nothing. I replaced the bearings and the problem disappeared . I don't know exactly what the problem was with a bearing but the rotation of a bearing will bring any given ball or roller around to the same spot on 2 revolutions.
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