There is a ring at the very bottom of the quill. This holds the bearings in the quill, and applies the preload to the bearings by pressing the outer races against a ground spacer between them. You really don't want to mess with this unless there is a problem.
Your problem (if any) was the bearings at the top, on the spindle pulley, not the spindle itself. So, I don't think Tom's info is relevant to it at all. I can't see how the bottom bearing preload would affect the driven pulley bearings.
To Tom, I believe Iggy is referring to bearings J-293 in the 1J head drawings, part # 1190232, listed as #207 bearings. And, actually, these bearings may not have been getting hot at all, it may have all been pulley heat.