I would say not possible
Even using cobalt drills
I remember them on BMC engine blocks
They were like hammer in self tappers
I am sure i have some at work
John
Absolutely hard to drill even with carbide. They are small and if you do manage to get a drill bit started it will walk all over the place. A new hole is the only way I know of. As said these little buggers are hard.
"Billy G"
These were hammered into the mill in 1969/1970 so have had plenty of time to get stuck in there!
I will continue to try the slot and turn method, as I may get lucky with a few. Those that put up resistance will be dealt with by drilling around them.
If you're planning on doing a full-on paint job, you could carefully heat them, being careful not to damage the plate. If the plate is a silkscreen job this won't work without damage. For thicker plated, with a small flame, you can bring the rivets to a high enough temperature to soften them a bit.
If you drill with carbide, be mindful of the brittle nature of it. And yes, they have to be hardened to work the way they are intended.
Unfortunately, they are all silkscreened. Hmmmmm, wonder if I could build a small EDM
A handheld spark eroder. I don't see why not.