would appreciate someone telling me what the tool is called so I can have an informed chat with a shop or framebuilder
If you're talking to a framebuilder, they will know which tool they use for spotfacing, probably just an appropriately sized end mill, and the same (but smaller, obviously) for the counterbore which takes the tube nut.
If you're talking to a framebuilder, they will know which tool they use for spotfacing, probably just an appropriately sized end mill, and the same (but smaller, obviously) for the counterbore which takes the tube nut.