you can not really make a solid there was a C-hook a while back I have to check my archives for it or the Mastercam forum FTP that would take the stl file and change ti surfaces. but if I were to make the thread with the solid I would create the helix and then the profile of the pitch and Solids sweep to create the tread.
(Note: The opinions expressed in this post are my own and are not necessarily those of CNCzone and its management)
Cadcam
Software and hardware sales, contract Programming and Consultant , Cad-Cam Instructor .