The type of repair depends on the type of thread.
For a straight thread (with a gasket seal), install a helicoil of the proper thread.
For a tapered (pipe) thread, tap to a larger size, and fabricate an insert plug with a flange and a gasket. Tap the insert for the pipe thread. Install the insert with a couple of drops of red loctite on the insert threads. Let set for 24 hours and then install the original fitting in the insert.
I used to make the comment that only plumbers would use teflon, until my father (who has done a LOT of plumbing) informed me that no competent plumber would ever consider the stuff.
The only really GOOD use for teflon tape is to put on stakes you put by newly planted trees. The teflon tape flutters in the breeze, and the individual using the lawnmower does not mow down the trees! (MOO)
Jon.
