Hi, I see. In fact, I am using many different objects, not just a sphere. I mentioned the SCNSphere as an example; I thought it would not make any significant difference. I see your point now; it does seem that for some objects the bbox can be off center, but that happens to be okay for my use case. I will go ahead and accept your initial answer as that did solve the issue I was having. Thank you!

Thanks for the detail! Although for some reason, if I apply a rotation to the object after shifting its position as above, it seems like the pivot for the rotations does not quite lie in the center of the object anymore.