"rrh" wrote in message
...
Carefully heat the chuck with a blowlamp in the hope that it will expand
more quickly than the bit so the latter will come out? Don't know what
this
might do to the properties of the metal the chuck is made of though.


Perhaps with a 'slight' strain on it by holding the outer part of chuck in
the bench vise, twist and try a slight tap with a light hammer.
Suspect jaws of chuck may have snugged up against bottom edge of the
countersink head and jammed?
Alternatively can you hold the countersink it self in the bench vise and try
tapping the outer ring of the chuck with a drift punch? Or even turn with a
pipe wrench, after all you gotta. get it out somehow otherwise drill is no
good for anything else?