When you say 'dialed it in' can you elaborate on your test setup?
- as in confirming tailstock deviation of in/out vs. up/down from headstock spindle axis?
- where was the DTI located? (I can visualize the indicator mounted on a rotating headstock part & confirming tailstock axis alignment in close range.. but how would you have accomplished this with the tailstock positioned way out at the end of the lathe?)
- assume you are using a DTI vs dial gage? Some people have reported variations of the dial gage plungers when pointing up vs. down (maybe spring loading or gravity acting variations?)
I found chasing-my-tail variations when checking my tailstock setup. Amazing how 1-2 thou can creep into mix that had nothing to do with axis alignment. Examples: Chucking a dowel pin in tailstock chuck is asking for trouble because chuck's runout/grip will likely vary even with a precision model. I think inserting an accurately ground MT collet with dowel or an MT arbor with extended stub & indicating around that is less error prone. And even with that probably best to leave in same position throughout tests for consistency & remember to lock the travel spindle the same. Check that tailstock underside is 100% clean of slightest particle debris. Check for edge casting burrs or anything that might cause variation & use consistent tailstock clamping pressure.
I've been tempted to get one of these precision ground MT/straight test bars, but I'm not exactly sure of proper usage / implementation. Does one set in tailstock & now the (long extension) magnifies tailstock deviation by indicating around the end from headstock mounted DTI? I thought another use might be to insert in headstock (with MT5/MT3 adapter) as a means of validating head alignment to lathe beds & carriage travel or setting up taper turning angle zero datum, but I'm not sure that would give me better results than what I'm doing now.