Bill wrote:
I am looking for a 5/16 drill bit, probably a brad point (it needs to
drill, with very little wander, through end grain of tamarind and ash),
with about 6" of flute (likely about 8" OAL) to let me insert a piece of
O-1 rod through a handle and into a rolling pin for reinforcement.

My first thought is to use bradpoint of Forstner to start and then that
for guide for deeper w/ twist or augur.....