how to make internal and External Thread on bottel Neck

If you want to make internal or external thread on bottel neck you have to use two commands that is "Helix" and "Sweep".
You can find helix in curve section in NX and sweep tool can be find in home section, and now there is no need to explain that where is curve section and where is home section.
In helix you have to describe diameter or pitch for thread and location where you want put helix,
and then go to home section first of all you have to create a profile for thread.
For creating a profile you have put a datum plan on a helix's first or end point.
Now exit the sketch use sweep tool then select profile and guide curve which is you helix and at the last option of you dialoge box that is boolean operation select subtract. Then ok.

Boss/Extrude and Extrude Cut options will definitely help you

See, there is a direct command in NX for Thread Designing in part modeling and it's very simple to create it.

direct thread option is there in there itserlf...