Hi @ctoicqtao Welcome to the Forum 
Regarding Threads you may find this useful:
https://discourse.shapr3d.com/t/generating-threads/6680/2
The above applies to External and Internal Threads you will have to make adjustments as necessary.
If you need more help just shout.
The S3D Team and Members are always ready to help.
Due to other commitments do not expect any responses from me for several days.
Happy S3Ding