I made up some old style soldering irons for the job. I took some copper rod and spun it in the lathe just under bore size and threaded one end. I then attached it to some 1/4" rod threaded to match and welded two of them side by side to fit in the bores. I put the whole unit into a wooden handle and it works well when heated with an acetylene torch. I use kester brand rosin flux and am careful to not over heat it.

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