My shower arm had broken off and the threads were still inside that nut. I went to Home Depot , got one of those thread removers. I got big hunks out and it seemed to be clean. I went to put in the new arm, put the teflon tape on, but I can get it to turn only 2 and a half times ( about half the thread of the arm) and it drips. So I peered in the nut again and either I stripped the nut in the rear threads or theres still a sliver in that back thread. But...Im not sure if that smooth ring at the rear thread is just where the pipe meets the nut. Either way it looks rough and seems to be stopping the arm from screwing all the way in. The thread rermoval tool cant get a good grip on that rear thread plus i dont wanna make more of a mess. I really wanted to avoid ripping walls up..any suggestions guys? Or maybe its only supposed to turn in only 2 and a half turns and I didnt teflon good enuf?