I've been holding off on help as I thought someone with more knowledge then me would have chimed in by now. But here goes.
I think you have to look at this just like you would for re-homing after battery failure on a positional axis like X or Z. The hard part is you can't do the easy thing like you can on a positional axis where you put the axis exactly where you want it and flip the parameter 1815.4 bit from 0 to 1. (Or vise versa?) That's because I have no idea how to rotate the turret manually in small movements like you can on an axis with a remote handle available. So in short I think you're stuck with calculating the grid shift amount for the turret. Those in the know might be able to give you the exact math to use. All I know is parameter 1850 holds the grid shift for your turret and everything else. Could be a lot of trial and error. You might have to P/CANCEL during re-boot after every unsuccessful attempt before trying again.
You'll want to mount a bore or pin you can indicate to as you try your luck at getting the grid shift to put the tool dead on in X in relation to the spindle bore. Come to think of it, measuring from a fixed X location once found, that could be considered a theoretical Y position you're after with the turret rotation.
After reading my own suggestion, I think a call to Mori would be a great place to start. Could save hours of hit and miss. I'm sure the people on the machine assembly line in Japan aren't doing anything like that described above. Which is likely food for thought at best.
Dave
