You could also try sharpening the drill? Sharp drill, zero rake so it doesn’t grab, get the revs up, lots of coolant or proper RTD, clamp securely in a vice and press hard on the drill press.
Its more likely to be work hardening than anything else. Heat to red, hold it there for a few minutes, and then allow to air cool. should soften it.- or do I understand its actually a part of the boiler already?
If its already a part of the boiler, then go back to para 1 -can you get this thing into the drill press or milling machine? If not, then its a good sharp zero rake drill and press HARD.- don’t let it rub. Once it starts to cut, you will be well away.
Tried a small pilot diameter?