An oil transfer assembly supplies oil into a moving, rotating tube extending along an axis. The assembly is provided with a support plate transversal to the axis and a sleeve, which is angularly fixed with respect to the support plate, it is configured to be coupled in a sliding and watertight way to a terminal section of the inlet of said tube and has at least one chamber for transferring oil into said terminal section of the inlet. The assembly is also equipped with at least two tubular bodies, which project axially from the support plate, define between them an annular channel communicating with the chamber and join the sleeve to the support plate in a watertight manner and with clearances so as to leave freedom of orientation of the sleeve around any direction orthogonal to the axis.