there should be a set screw in the side of the lower half that provides friction to adjust how easy/hard the top turns. if you back it out far enough, or remove it entirely, the upper section should lift straight off.
Just trying to help.
Not trying to be a critic but I notice some pry marks on the side of your vise.
Be sure to polish or burnish down any metal that is raised on these edges or your ball vise won't rotate smoothly. Best of luck with what you are trying to do.
Thanks, know what you mean and will polish these areas. But this vise won’t rotate anymore. I will fix it at a 6“ ø x 0.8“ stainless steel plate (nice weight ) Should be placed with a non-slip coating on my turntable of same dimension (all together very nice weight )
The idea was to transform that relatively light ball vise into very flat and very stable positioning vise without need of loosening and tightening any handle.
Hope items will always stay horizontal without drifting while cutting