dadiOH wrote:
Heat.

I once had to replace a 1/2" chain plate bolt that was through the
stem of my sailboat. Wouldn't budge no way, no how even with a
sledge. Heating it with a propane torch freed it up. Heat your
little suckers red hot and they'll come out even if you have to char
the hole they are in slightly.
Alternatively, you might try sticking the mallet in a freezer for a
while.

Ditto. If in doubt, burn it out.

Jon