A gas turbine engine rotor (14), including: a rotor disk (16) comprising a bolt hole (82) there through and a counterbore (86); a bolt (18) configured to fit in the bolt hole and when so disposed to define an end (72) protruding beyond the counterbore; and a nut (84) configured to be disposed in the counterbore and to engage the protruding end. The counterbore is configured to permit limited eccentricity between the nut and the protruding end.