I made a ball joint like that for a camera mount many years ago. I used a 1" ball, so similar size to yours.
To make the "bell" part I simply drilled with a 1" drill from the rear and the countersunk end of the hole was sufficient to retain the ball and to allow it to move around. When the ball was locked the small contact area of ball to the "bell" was sufficient.
I enjoy your videos Keld, thanks.