now what?

The column is now vertical (within acceptable limits).
- DTI held in headstock via collet, tramming up & down a right-angle (1-2-3 block) sitting on table.
The dovetail mount is parallel to the Z-axis travel.
- DTI held on table, clocking off bearing face of dovetail
The ER16 headstock is clamped to the dovetail and the vertical (fixed) face of the headstock body is parallel with the Z-axis.
- DTI held on table, clocking off fixed face of headstock body.

However, the spindle axis does not appear to be parallel with the Z-axis.

When sweeping the table with the DTI over a 10" radius, a difference of .006" is registered between the tops of the 1-2-3 blocks on each side of the table.

Possible sources of the error:
- ER16 spindle ball-bearing bores not parallel to bearing face of dovetail
- dovetail mount not true
- buildup of measuring errors

A 5/16" piece of drill rod through a collet gave visual indication that the spindle was, indeed, slightly off vertical compared to a square on the table itself.

The whole purpose of the tramming the mill is to ensure that the cutter is running truly and the headstock moves accurately with respect to all axes of traverse.

A simple expedient to deal with this last error is to snug up the dovetail mount cap screws and tweak the headstock while sweeping the table, then re-tighten the cap screws. Luckily the SHCS's are accessible with the headstock mounted.

Should be OK to go ahead and re-mount the motor and start cutting again, but these errors and faults will all need proper correction (possibly through re-machining or grinding) at some later stage in the game...