Geat pieces, are you using a full size router freehand, still trying to picture this. Is the piece still on the lathe at the time of routing? I still see my piece going caboom
I'm using a laminate trimmer mounted in a sled, which slides on a table attached to the lathe bed. I've mounted an index/drive wheel to the outboard side of the spindle. A cable is wound around the index/drive wheel and goes through a pully system and is attached to the sled.
As the index/drive wheel is turned, the sled is pulled along the table and the piece, of course, rotates. The result is a spiral. The system I use is similar to one which was posted on WoW a while ago.