You cant use them on metal. The ones I use look like a smaller stub of a drill bit on the front of a larger bit. Cant find a picture of it for some reason. I get them from surplus city.
Pilot tip... I think B&D called theirs Bullet drills. Have an old set somewhere. I liked the way the spot cutters worked on mine. Doesn't go too deep in the center metal. But yes, the tradeoff is you have to grind some away.