I have a small problem. I was silly enough to expect that when I put a couple of wrenches on the three "nuts and bolts" on my chain wheel, that they would unscrew and come off. Nope. They spin both directions if I want, but do not come off. It seems like more of a rivet system. The bolt side is 7/16" and the nut side is 1/2". Any ideas what is going on here? Also, does anyone know what the other fasteners are called? They are tubular threaded fasteners. In the picture I show three of the six.
Thanks,
Marv

The three bolts and nuts loose are called chainring bolts. But the other three that attach the ring to the spider arms are also called chainring bolts, terms vary from brand to era. Riveted rings, onto the spider, are rather common still. These days a sign of production cost reductions VS easier to service designs. As long as the rivets/bolts don't creak/tick all is fine.

BTW there's a lot of on line groups that focus on collector bikes and Schwinns in general. Andy

Thanks for the quick response. I kinda figured that's how they worked. I just had not heard of that before. They cleaned up pretty nice. Now they just need some fine sanding and some polish.
Thanks
Marv

I wouldn't sand it - fine steel wool removes dirt and corrosion without leaving scratches that have to be polished out.