I have a manual lathe in my show with a D1-5 Camlock spindle nose. I have several chucks including a collet chuck and a three-jaw that are set up with the D1-5 backplates.

I also have a home-built 4th axis for my milling machine. The 4th is built from the headstock of an old harbor freight mini lathe. If I recall correctly, that's 1-1/2 x 8TPI. I don't have any chucks for the 4th axis yet and would rather not buy if I don't have to. I've looked all over for an adapter that would let me use my existing chucks on the 4th axis without remounting them on different backplates. Does such a thing exist?

I don't do any precision work. Mostly I develop the CAM workbench for FreeCAD and I use my equipment for testing toolpaths and basic hobby stuff. So I'm not concerned with hitting tight tolerance.