How is this the wrong forum, its a CNC programming related question?.
All turning tools are set up to the centerline.
If you need to learn how to write a threading Canned Cycle, look at youtube, put in my name: Heinz Putz, to see a DVD to start learning.
In my job as an independent CNC trainer, I have made many, many pipe threads for Oilfield parts, in cluding one foe a 3000 HP motor for a company in Corpus Christi, that was real fun.
Heinz, doccnc.com.