The holes are just drilled 8.5mm through and then where the ball sits is 11.5 for the 12mm ball. The drill provides a taper like seat for the ball and no 'O' Ring is used. The screw is tightened to hold it in the desired position, so once adjusted the screw is just nipped up tight. Oh and its a countersunk head setscrew which hopefully gives a wee bit more contact are on the ball for securing position.
The feeds in the vid for delrin part are too slow thats for sure, roughing cuts were 0.25 and finishing 0.15 if I recall. The finishing tool is 0.2 rad so dont want to go much faster on that but the roughing I could have doubled at least. The threading also could be done in just a couple or three passes I suppose but I am in no big rush really. The code was written originally for stainless as that was what it was originally made from so threading was about right for it.
On the manual lathe I regulary tak very deep DOC in delrin, usiually 10mm or more per pass but I tend to be more conservative with the CNC, not sure why, probably just because it gets on with things whilst I do other things so there is no real rush.
Ah yes, it was my workbench whilst doing this, its all cleaned up now though and the Conect lathe, Student lathe and Bridgeport mill are now my workbench
Hood