• A good dealer can do that for you for relatively low cost (considering that the frame is worth it).
    No need for brazing or welding.
    Can be done fro all steel, alu or carbon frames without replaceable derailleur hanger, as long a the droput is not cracked and it's not bent too much (steel is very forgiving, alu and carbon not).

    Dealer should have a reamer of the correct size and a threaded metal piece, that will be glued in place.

    Dill dropout to remove old threads
    Ream drilled hole to make correct diameter
    Glue and place threaded insert
    Check / correct alignment with dropout / rear derailleur hanger alignment tools
    Job done

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