Bobbin Part Chuck Adapters

thingiverse

You can use these to connect the two bobbin parts (A & B) directly to a drill press chuck, ensuring that the roundness is accurately true after printing or enlarging holes with decent speed concentrically. The finish on vertical surfaces must be very good since these are a tight fit but bridging and support areas can have a little mess without significant ill effects. They feature a 1/2-inch shank about an inch long. https://www.tinkercad.com/things/iwe0w6CnQwf