Today was a side line project - I need to be able to make 3/4" holes in the ribs which requires the angle adapter - however the unitbit and rotorbroachs don't have a 1/4" screw thread.
After a couple of trial runs, I ended up turning two old bolts down on the lathe and made a simple adapter, although it took a bit longer than expected.
The finished tool - rather than a clever drill center I just used a #19 pilot stub.