I have a lathe that is chattering during the final cut of a 2 cut process. The part is a 18.5" Barake drum. Chatter generally occurs due to tooling ass'y. issues or ball screw and bearing issues and occurs at the outermost portion of the part. This chatter is occuring at the middle and innermost portion of the part.
-All tooling is tight and installed correctly.
-All Bearings and ball screws are in good shape.
-The spindle is running true.

Any thoughts on where to look?