Is this curve in your file a path that you want the protrusion to follow? :



I set up some profile curves to do a sweep using that path as the sweep rail:

The idea is to make the protrusion modeled as a separate object to sink down into the ring so they can be booleaned with each other and then put a fillet on it:





But like I was saying before if the protrusion is vertical it is not over the ring and will go off of it:





- Michael