creating something like an expanding ring mandrel for my homemade lathe I am crafting my own drill powered lathe so I can improve my ring making. The problem is, even though I can make a working lathe, I do not have a way to securely place the ring in the lathe to make it fit snug like I could with an expanding ring mandrel. The expanding ring mandrel does not fit inside of my current drill so I have to use alternative methods. I like crafting things with my own hands, and this ring mandrel is just another step in the fun process of starting a new hobby. Anyone have any ideas on how I can make this work? My drill can open it's jaws up to 1/3" I believe.

Video for reference on how I will create my lathe.
https://youtu.be/KmpdEtvVRfI

How an expanding mandrel works. 7:08
https://youtu.be/iiFIfKikJRM?t=428
Making one properly without a (metalworking) lathe would be very difficult.  With one it's quite easy.

This youtube video shows one made from simple hardware, and you could choose an appropriate screw for the shaft to fit your chuck.  But I'm not sure I'd trust its centration (might not matter if you're just using it like the second video link).

It may be possible to replace the chuck on your drill with a 1/2" version.  Then you could buy and off-the-shelf ring mandrel.  1/3" is uncommon, though 3/8" or 10&nbsp;mm is quite common on battery drills, and I have a hand drill with a 1/4" chuck.