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 .