I just removed an old shower arm with surface rust. Our house is from the 1950s and the piping in the wall is still OK. The threads were stripped at the end of the shower, and there was a spirally piece of brass that had been curled off the end because the previous installer had forced it into the female threaded pipe in the wall.
I put a new shower arm and discovered that it would not fit and that if I forced it, a strip of brass of the new arm would probably begin to "uncurl" just like the old one. The threaded diameter appears to be slightly smaller than the 1/2" standard or maybe the thread count is very different.
I suspect the female threaded pipe in the wall has a thread that is different than modern shower arims. It might be metric (?) but I doubt it.
Does anybody know what type of threaded pipe might be in my wall, and if adapters are available?