Michael,
You have a customer.

Yes, I am using Rhino's tutorials for jewelry, (very slowly....) but do not see how I can do tapered shanks, in addition it is more technical than MOI, and I have to re-think in simpler form.....therefore I have to.....I guess....to become better in CAD (I know, probably for you guys it sounds like a joke all this ...)
anyway, waiting for some more replies.
Thank you again Michael.
Good night.