JPG wrote
With the way tubes locked down, the critical thing is the 'angle' across the two way tubes is the same at both ends(twist). That big set screw is adjusted to achieve that.
A way to check that is the tailstock center point aligning with a drive center point on the quill, then moving the drive center to the top aux shaft and moving the tailstock to the other end. If the points do not align(front to rear), the way tubes are 'twisted'.
I’ll have to wait until I get the headstock refurbished to do that test. I did put a level across the way tubes at each end and they were the same.
