They look more like a spiral drill bit with a tap at the middle rather than what Cory posted. Best picture I could find was this one
I found a site that
had the speed calculations I was really after
For mild steel pipe and the 1/4" size hole/tap I needed to go ~30 RPM.
After I did the project with a hand tap, I did try the drill/tap just as a learning point for me. In a press, it was easy peasey to drill the hole and then tap right behind it at a slow speed. Needing to be able to reverse is a key thing.
Unlikely I would have been successful out in the yard doing this with a hand drill.
And if I could afford a Tapmatic head at $350, I'd be lots smarter than I am and would have done this before I sank the pipe into 350lbs of concrete.
Thanks again to all that replied.