"Michael Gray" wrote: (clip) I could move the hole over and retap, but it
would throw off the symmetry
of the piece)
^^^^^^^^^^^^^^^^^^^^^
Or you could drill out or core out an oversize hole, and then press in a
piece of bronze rod. Thisw would allow you to retap without losing the
symmetry.

Or how about heating the piece enough to anneal the broken tap, and then
drill it out?