Re: Drilling hardened steel
More like 62-64 hrc. Masonry bits are much tougher than solid carbide twist drills. Won't drill as accurate hole, but have a good chance of getting through it without breaking. But give the twist drill a try and see how it works. A sinker EDM would be my first choice if you have one in your back pocket.
There is another way, copper tubing and some course valve grinding compound, or diamond dust. Will actually drill through hardened steel or glass.
Jim Dawson
Sandy, Oregon, USA