I broke a tap on a puma lathe with a fanuc 18t control, when I touched off the new tap I noticed the geometry number was over 3 inches off, I then noticed the G54 Z0 was way off, and I could not home the machine (over travel) what do you think? ball screw,endcoader?? I dont know if these machines have a clutch on the ball screw or not? any help would be great

Yes, there is an overload clutch on the Z ball screw. You probably heard a wierd 'thump-thump' noise when the tap broke. That was the clutch doing it's thing. It should fault the machine out when it trips, but ours has jumped without doing so at least once or twice...

Re-homing Z (ref. return) is generally all that is required to get your Z numbers back.

At first I cursed the clutch in our machine (it has tripped from just pushing a big drill too hard), but now five years on, I'm thankful for them. We have never had a crash that we could not recover from (knock on wood) ourselves.

Thats what it was,I didn't hear the thumping though, I was tending another machine, no alarms or anything, Im not use to the clucth thing, but I can see how it could be a good thing, thanks for the reply

I assume you figured out how to inhibit the overtravel limit to home the machine (sorry, I missed that in your original post). I always have to look that up in the Fanuc manual...