Brent:
Below is a link to Aaron's Cap Screws. They carry a selection of bound frame bolts in grade 8.
http://www.aaronscapscrews.com/search_frame_bolts.htm I'm not convinced manufacturers don't use hot rivets for speed on the assembly line as they use them for many parts on the frame where strength would not be an issue.
I could be wrong after all, I'm married...
