Help from a pro please!
I'm replacing a bathroom sink in an old house. The previous sink drain had been poorly installed--the tail piece from the sink had been "caulked" into the cast iron T in the wall. When I removed the old tail piece, I realized the cast iron T either never had threads, or they had long ago rusted away. I am left with a cast iron drain nipple that has a rusty round hole in it. So--is there any way to retrofit a fitting into this hole to create a tight, professional connection between the cast iron drain and the new PVC sink tail piece? Is there such a thing as re-tapping the threads?

I'd just love to avoid having to tear out the wall and install new drain line if I can avoid it. Thanks for whatever anyone can offer!