I learned that trick several decades ago. We all probably learned early on that common twist drills make tri-lobular holes in thin metal. I learned how to grind a bit to make a round hole from others, a trade secret passed down for generations, I suppose. The tip looks a lot like a brad point drill for wood working. The best off the shelf bits that work well for sheet metal and about everything else are Black & Decker Bullet Point drills. As was said, Unibits also work well, but it is easy to misjudge the RPM and burn them on steel or stainless.