The cap blank was drilled part of the way and a dowell was inserted and glued the size of the cap hole vacated by the stock insert. I glued the dowell in place at the sacrificial end of the blank only. On the other end of that blank I screwed into a hole my bottle stopper mandrel which was driven by a drill chuck in the head stock and a live center on the tail stock. It was turned finished and removed from the blank and was inserted and glued to the cap from the inside with gorilla glue.
I hope that helps, any easier or better ideas would be appreciated.
Glenn