Quote Originally Posted by Frank S View Post
It is an expanding mandrel much like you would find to expand an exhaust pipe. if you stop the video at the 1,03 you can just see the lines showing the segments. the o rings would be used to draw the segments together when released by the spanner.
A truly nice set up though. Fast and repeatable
I don't think there are any reliefs in the metal allowing it to expand. I think it's just a sleeve. He's got a couple links in the description of the Youtube video where he has some additional information.

https://drive.google.com/file/d/1bLt...6F0li-IRw/view
https://drive.google.com/file/d/1hBh...Ah_NWyclF/view