I need some help with modeling the threading of the cast iron housing you may have seen Cutting a Cast Iron Housing
1. The pitch of the thread is 5.70 mm, but how would one make a seamless thread with different profile geometries (see below circled in blue)?
2. FADING AT THE TOP
the top thread fades/merges into the black trough. They then fade/merge together into the white portion (watch the blue lines I've drawn in the 3 images below)
(below) the thread is no longer visible, the white portion is flat
What I have so far is the basic threading with the proper pitch but I don't have the "FADING/MERGING" or the thread profiles down.