I am looking for a bolt that is approx. 1/2" or 3/8" long x 1/4-20 thread but the head looks like a rivit. I want to know what they are called and where to buy them
no, no square shoulder they are not carrage bolts , i have herd them called huck bolts. that bare metal rpu called the a-bomber has them all over it
Rogue did a bare metal rpu a couple years ago,using bolts like you describe. He called them "locker bolts",used to bolt storage lockers together. Unfortunately,his supply got depleted,and the source dried up.
http://www.portlandbolt.com/products/buttonhead.html Those are called Button Head Bolts. Click on the above link.
it sounds as tho you are looking for a security fastner either a hex or square hole with a small dowel type in center. You live in CA so check for a fastenal fastener wharehouse as said before www.mcmaster.com is good
i'll second the "locker bolt" name, don't know if that official though. the ones he is looking for are not button head or security bolts, they have nothing on the head but a smooth dome, and are serrated under the head to grip the piece you are bolting to keep from turning.
Looks like the same ones I found but a different place. http://www.langequip.com/Merchant2/merchant.mv?Screen=CTGY&Category_Code=LPR-LHH