"Stuart Wheaton" wrote in message ...

Drilling into the end of a large threaded rod, centered, punched and
drilled starting at 1/8" worked up to 3/8". 3/8" is about 1/4 of the
way into the hole and quit cutting, Either I hit a hard spot in the
steel, or it got work hardened, I was using coolant, but not flood.

Swapped to a new and sharp HSS bit, no joy at all.

Suggestions?

snip

Silly question, but are you certain it's not stainless studding? That can
work harden if you back off pressure when drilling.

JB