The subject tells it all. I've gone nearly blind googling for such a
thing so perhaps if someone knows of a supplier they could help.

I'm converting an old chandelier from candelabra bulbs and fittings to
regular medium base sockets. At the end of each arm there's a 4 inch
1/8" nipple brazed into the arm. I plan on cutting the nipple to about
1" with a hacksaw and anticipate some thread damage so I'd like to be
equipped to reform the thread.

Everyone (including my local hardware store) sells NPT but this is a
tapered thread and I need a straight thread aka a "National Standard
Free-fitting Mechanical Pipe Thread".