Does any know if it is possible to peck tap on a Mori Seiki lathe NLX2500 (Mitsubishi control) with live tooling rigid tapping mode (G84)? Also is possible to tap a hole (rigid tap) return home index re-drill the hole and then come back and re-tap the same hole? I know Z cannot change start point.
While I'm not familiar at all with that machine or control, I'm wagering that you don't have a rotary position control on the live tool spindle like you do on the main spindle.
A simple test would be to put a piece of plastic in the chuck, load a single point ID threading bar in the live spindle, and back it off in X so that it takes shallow cuts (we'll be gentle on the tool).....
Drill the part, thread it, then repeat the cycle and see if the tool follows the same pitch.
Then, if that works, try the re-drill and re-tap..... I wouldn't be too optimistic..but it's a cheap way to find out, and it shouldn't take very long. And you're only out a piece of plastic!