Forgive me for stating what you probably will find obvious. I
followed this thread awhile back too. I never approach a broken drill
chemically. I suppose the reason is: I can’t wait that long!
Do your level best to bur a small depression aligned with the drill.
Use a drill smaller than the broken one to drill perpendicular to the
broken one. When the drill dulls and you are in line with the broken
drill; make a drift punch out of an old bur shank, and punch or push
Assuming you can’t access the area, for the prior solution; here is
another idea. Bur the hole with a ball bur; carefully staying aligned
with the broken drill. Bend a drill by heating red hot and bending at
an angle. Form a suitable shape to reach the hole you have burred.
You could sharpen the end to cut if it will help. Put the bent drill
in a pair of pliers (parallel, chain nose, etc.) or pin vise. You may
be able to push it out. Drop a little oil in the broken drill hole.
Hope I haven’t wasted your time reasding this!
To remove a drill usually takes the time of setting several stones. It
is always a real pain. Good luck. Tim