Had an intresting discussion about creating a core and cavity on a part. It is kind of hard to explain but I will do my best. -Using the revolve feature, draw a shape so that when you are done it looks like it has a half sphere at the top, and lines coming off of it and close it off at the bottom so that it would be able to stand on its own. (if you think of a key hole of a jewelery chest that is just a basic shape from the front view) - Once it is revolved, if you were to say use split line to split the surface in half, create a parting line off of that, and then say use a ruled surface at the 3* draft outwards. - If you spin the model around you will see that the ruled surface and the upper half of the mold would not be a smooth tangent transition. I hope that I explained it well enough for anyone here to figure our a solutions
tia