Bicycle Mechanics - Problem with built-in derailleur hanger

The threads of the built-in derailleur hanger on my 1980s steel frame appear to have stripped, such that it's impossible to get the RD in tightly except at a slight angle. What's the best way forward from here. I was thinking of grinding off the hanger and replacing it with an adaptor. Does that sound reasonable?

The threads of the built-in derailleur hanger on my 1980s steel frame appear to have stripped, such that it's impossible to get the RD in tightly except at a slight angle. What's the best way forward from here. I was thinking of grinding off the hanger and replacing it with an adaptor. Does that sound reasonable?

replacing it with an adaptor is certainly a solution. if you can thread the derailer in all the way and have it be secure, you might also be able to "straighten" the hanger with the proper tool (park tool DAG-1). i put it in quotation marks because it wouldn't actually be straight, you'd only be aligning the threads of the hanger with the cassette.
if you can't thread the derailer in all the way, then you might have enough good threads chase the cross threaded section.

The simpliest solution is called a "drop out saver". It's a T-nut that is specially designed to replace the threads in your hanger. Bike shops should have them.

http://www.biketoolsetc.com/index.cgi?id=98212742410&d=single&c=Shop-Aids&sc=Thread-Repair&tc=Thread-Inserts&item_id=WB-DS1

Try using one of these instead

http://www.loosescrews.com/index.cgi?d=single&c=Misc&sc=Dropouts/Braze%20Ons&tc=Thread%20Repair&item_id=WB-DS2&id=82363953897

Edit: I see Dirtdrop beat me to the punch, and his is cheaper!

http://www.biketoolsetc.com/index.cgi?id=98212742410&d=single&c=shop-aids&sc=thread-repair&tc=thread-inserts&item_id=wb-ds1

bingo!

Thanks to one and all. That looks just the ticket. Never knew such a thing existed!