"J. Clarke" wrote

Drilled a dozen pieces 3 inches deep, drill continues to cut fine, so am
assuming that yellow is something coming out of the Ash and not indicative
of the bit losing temper.

Wow, I just realized how deep you are drilling. Drilling that deep in hard
stuff would be bound to heat the bit.

Try a closely directed stream of compressed air on the bit. Cool that
sucker with air, and slow down the drilling process if the burning is
objectionable.
--
Jim in NC