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?
You still have more of the shower arm stuck in the drop eared elbow.
I usually get them out through the existing hole in the wall or, make it slightly larger but still small enough that the escutchion will cover it then by catching a piece of the thread and break it inward then grab it with pliers or, small vise grips continue round and round carefully breaking it inward without breaking it off. Kinda like opening a sardine can... It ends up looking like a helicoil and it comes out. Hopefully this works for you, there are other more expensive methods if this doesn't work.
On the siouxchief website http://www.siouxchief.com/Frm_MS.cfm click specialties, then tools... Scroll down to "Internal Nipple Wrench" That is another tool that may work.
Another way that I get them out is by using a #7 easy out with 1/2" cut off the end.
If you can get it using the first method you don't have to buy any tools.