I'd personally use the 3 screws on the main shaft to adjust it.

Physically centring a probe is something I've never done, as I always calibrate them in software. On the digitiser, that is done simply to allow for any inconsistencies in the tip/switching, where as on the mill is done to allow for any inconsistencies and to ensure they are known relative to the spindle centreline.


If you've got an old style edge finder, I'd just use it like it was meant. Jog up until it wanders, then subtract/add half the diameter from the position, and you're done. Saves having to centre the edge finder and connecting a crocodile clip.