A locking device (300, 310) comprising: - a shaft comprising a first external thread, and - a nut (12, 112, 212) and a ring (13, 113, 213) to be assembled on the shaft; the nut (12, 112, 212) comprising a first internal thread adapted to mate with the first external thread of the shaft, said first internal and external threads defining a first radial clearance; the nut further comprising a second internal thread in the opposite direction to the first internal thread, the first and second internal threads being coaxial, an outer surface of the ring (13, 113, 213) comprising a second external thread adapted to mate with the second internal thread of the nut, said second internal and external threads defining a second radial clearance; an inner surface of said ring having a third internal thread adapted to mate with the first external thread of the shaft, said first external and third internal threads defining a third radial clearance; characterised in that: - the first, second and third internal threads and the first and second external threads have an identical and constant thread pitch; and - each of the second and third radial clearances is greater than the first radial clearance. - a shaft comprising a first external thread, and - a nut (12, 112, 212) and a ring (13, 113, 213) to be assembled on the shaft; the nut (12, 112, 212) comprising a first internal thread adapted to mate with the first external thread of the shaft, said first internal and external threads defining a first radial clearance; the nut further comprising a second internal thread in the opposite direction to the first internal thread, the first and second internal threads being coaxial, an outer surface of the ring (13, 113, 213) comprising a second external thread adapted to mate with the second internal thread of the nut, said second internal and external threads defining a second radial clearance; an inner surface of said ring having a third internal thread adapted to mate with the first external thread of the shaft, said first external and third internal threads defining a third radial clearance; characterised in that: - the first, second and third internal threads and the first and second external threads have an identical and constant thread pitch; and - each of the second and third radial clearances is greater than the first radial clearance. the nut further comprising a second internal thread in the opposite direction to the first internal thread, the first and second internal threads being coaxial, an outer surface of the ring (13, 113, 213) comprising a second external thread adapted to mate with the second internal thread of the nut, said second internal and external threads defining a second radial clearance; an inner surface of said ring having a third internal thread adapted to mate with the first external thread of the shaft, said first external and third internal threads defining a third radial clearance; characterised in that: - the first, second and third internal threads and the first and second external threads have an identical and constant thread pitch; and - each of the second and third radial clearances is greater than the first radial clearance. - the first, second and third internal threads and the first and second external threads have an identical and constant thread pitch; and - each of the second and third radial clearances is greater than the first radial clearance.