Thanks all!
i hadn’t considered the “tools over 7 inches” issue (though arguably a bolt is not a tool but something you use a tool with
) and if mini baseball bats won’t fly then I think the chances of a solid steel bolt flying as a carryon are nearly nil.
Though I’m timpted to check it sans box (probably but and bolt as two separate pieces) just to see looks on people’s faces at baggage claim (ala the guy in Australia who checked a single can of beer) based on how late were getting home/not wanting to wit at baggage claim, I think I’m just going to leave it with the relatives for now and get it the next time I’m driving all the way .