Originally Posted by
vintagerando
Something is stopping me from screwing in the cup on the non drive-train side. Of course this was by hand, no tools, with easy pressure.
It looks like there are some burrs, sharp metal fragments coming from where the chainstay tube meets the BB. Maybe that's what is catching. Could the end of the chainstay tube been disturbed the last time a bottom bracket was removed or installed?
Your pictures are all of the drive side, so they aren't much help. The BB wouldn't reach the chainstay until it is almost fully threaded in. Verify your BB is the same threading as the frame's BB shell. Then get the BB shell threads chased.