These are cheap and sold by HHIP, Accusize, HFS, SHARS, and whatever else Chinese companies.

The original mount only went up to a 1-7/8" spindle for a bridgeport style machine.

I made this fit snuggly on my 68mm spindle for my 6550 LittleMachineShop (Sieg SX2.7) mill.

You need to make this out of something really stiff with high infill or it will just flex! I used PC and annealed it when the print was completed. In addition to that I filed a flat on to my spindle to ensure it doesn't move at all.

If you are having a problem with the arms coming loose when adjusting them all you need to do is rough up the male threads where the thumbscrews are seated, not a whole lot but just enough that you can turn the arm in both directions without it unscrewing itself. I just used a pair of pliers to grab onto the threads to rough them up, loctite would probably work too.

I modeled the washers but i haven't printed them. Everything else uses the original hardware