What is a good approach for creating a derivative casting and machined pair.  I have been creating a separate casting model (part) and then inserting the casting into a new part to create a machined model.  This works well until I want to create a derivative casting requiring a new casting part number.  I can open the casting part and do a 'save as' to capture my new design intent, but I am not aware of a way to create a derivative machined part (new part number) that starts with my prior machined part to save redoing many of the common features from the prior machined part design.

Any ideas?

Blair