Abstract: A detachable fitting device fits a mechanical component endowed with a cylindrical hole onto a shaft of circular section. The fitting device has an end collar having a substantially elliptical seat and a bush equipped with an elastically deformable external side surface for the reception of the shaft. The fitting is shaped to fit in the elliptical seat. The bush has a first size, measured along a straight line perpendicular to the axis of the bush, inclusive between minor and major diameters of the elliptical seat, and a second size, measured along a straight line perpendicular to the bush axis, which second side has a length which is less than the minor diameter of said elliptical seat.