An oil transfer assembly (31; 31a) to let lubricating oil flow from a stationary part to a rotating part, the assembly comprising: - a structure (29; 29a) fixed with respect to said stationary part and having at least one inlet (30; 30a) for receiving lubricating oil; - an interface member (34; 34a) adapted to be fixed to said rotating part so as to rotate about an axis and having: a) a front face (37; 37a); b) at least one duct (39; 39a) for conveying lubricating oil to said rotating part; - an annular chamber (36; 36a) which extends about said axis and puts said inlet (30; 30a) into communication with said duct (39; 39a); characterized in that - said duct extends starting from said front face (37; 37a); - said annular chamber is axially delimited, on one side, by said front face (37; 37a) and, on the other side, by a slide (35; 35a) which is coupled to said front face (37; 37a) so as to guarantee fluid-tightness of said annular chamber (36; 36a) and engages, in an axially sliding manner, a guide seat (33; 33a) provided in said structure (29; 29a); - said interface member comprises a front plate defining said front face and a supporting body; said front plate having: a) a radially external annular portion; b) a radially internal annular portion; and c) an intermediate annular portion, arranged radially between said radially external and radially internal annular portions (96, 97); - said radially external and radially internal annular portions (96, 97) resting axially against said supporting body in a radially more external area and in a radially more internal area, respectively, with respect to the sealing zones between said slide and said front face; characterised in that - said intermediate annular portion is axially spaced from said supporting body so as to deform under an axial thrust on said front face during use. - a structure (29; 29a) fixed with respect to said stationary part and having at least one inlet (30; 30a) for receiving lubricating oil; - an interface member (34; 34a) adapted to be fixed to said rotating part so as to rotate about an axis and having: a) a front face (37; 37a); b) at least one duct (39; 39a) for conveying lubricating oil to said rotating part; a) a front face (37; 37a); b) at least one duct (39; 39a) for conveying lubricating oil to said rotating part; - an annular chamber (36; 36a) which extends about said axis and puts said inlet (30; 30a) into communication with said duct (39; 39a); - said duct extends starting from said front face (37; 37a); - said annular chamber is axially delimited, on one side, by said front face (37; 37a) and, on the other side, by a slide (35; 35a) which is coupled to said front face (37; 37a) so as to guarantee fluid-tightness of said annular chamber (36; 36a) and engages, in an axially sliding manner, a guide seat (33; 33a) provided in said structure (29; 29a); - said interface member comprises a front plate defining said front face and a supporting body; said front plate having: a) a radially external annular portion; b) a radially internal annular portion; and c) an intermediate annular portion, arranged radially between said radially external and radially internal annular portions (96, 97); a) a radially external annular portion; b) a radially internal annular portion; and c) an intermediate annular portion, arranged radially between said radially external and radially internal annular portions (96, 97); - said radially external and radially internal annular portions (96, 97) resting axially against said supporting body in a radially more external area and in a radially more internal area, respectively, with respect to the sealing zones between said slide and said front face; characterised in that - said intermediate annular portion is axially spaced from said supporting body so as to deform under an axial thrust on said front face during use.