A couple decades ago, I ran across a handfull of self-tapping screws.
They were like sheet metal screws, but with skirted hex heads. These
were about 1/2" long and 1/4" dia. I'd seen them used with a special
head on a drill motor, it having a hex chuck that would ratchet when the
screw bottomed out. What amazed me about these was the fact they where
not only self-starting AND self-tapping, but they where pretty damn
hard. In experimenting, I discovered they tapped and screwed into an
old BSA motorcycle frame like it was soft pine.

I now find myself in need of something like this and was wondering just
what, exactly, do I ask for when I go down to the hardware store.

nb