What's the proper name for these bits!

I bought several of these along with a handful of square end bits for $1.00 each at a flea market.

This one is 5/16” on the small end and exactly what I needed to countersink 5/16" cap screws. I'd love to have several more sizes but can't seem to find them. I tried searching for step bits but the only results were the cone shaped bits for step drilling holes in sheet metal.

Thanks for any feedback.




Sent from my iPad using...

What's the proper name for these bits!