They look like some kind of end mill, but the geometry would suggest maybe a wood bit or for other soft materials. The clearance angles look too steep for steel.
I believe they're back face cutters also known as back face spot cutters. They're generally used the make a true flat spot on a plate or casting where the head of a fastener (typically a bolt head) will contact the material. They are also used to counter bore holes for fitting socket head bolts either slightly below or even with the surface.
Piloted counterbores usually require the through hole to be bored between 1/64" NS 1/32" oversize for the pilot to fit. Those without a pilot can be used without drilling the hole oversize.
This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
By continuing to use this site, you are consenting to our use of cookies.