I do all the machining in collets. If necessary, I use "emergency collets" and bore them to the required size. I hold the rough cast main shaft first and turn the tail shaft clean and to size. Then turn it around, holding the tail in the appropriate size collet, drill and tap for the cock screw and countersink slightly. Then bring up a long nose live center and place it in the screw hole countersink and turn the main shaft and face of the tumbler (and a raised anti friction ring, if desired). Turn the tumbler around one more time and finish off the back face and anti friction ring. Takes 10 minutes in a lathe.