Quote History Originally Posted By Deerhurst:
Endmill to make rivets? Use a lathe. It's the proper tool.
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I think he means what size ball endmill to divot a support plate for the head of the rivet itself. But could be wrong.
OP, you're going to have to go back probably a decade or more in searches on various forums to find a lot more specifics to building tooling. Seems to have fallen mostly out of favor now that AK-Builder, AKMACHINIST, Obstreperous, RForbus, Toth Tool, Requiem, Recreator, etc. are around and provide well built tools.