Trunnion plate for milling vise.

[Toolguy]

Toolmaker51-

I'm not sure if I'm understanding what you are trying to do, bu I'm wondering if bolting a vise to a vertical rotary table would get you there?

Edit to add: With the picture I see what you are wanting to do. A quality 6" rotary table with a tailstock or other outboard support might get you there. If using a tailstock, you could put a ball bearing on the T/S spindle, rather than using the point in a center hole. You could probably clamp the vise through the hole in the rotary table. That would keep the vise jaws away from the R/T out in the open. Now you have me thinking about building that.