A mandrel assembly for a tube bending machine has a mandrel body, a mandrel rod, a series of articulation elements connected to one another and to the mandrel body through respective cylindrical or spherical hinges, and a network of lubricant transport channels formed through the mandrel body and communicating with a lubricant feed passage formed along the mandrel rod. The network of lubricant transport channels has a plurality of lubricant outlet ports arranged on the distal end or on a peripheral surface of the mandrel body. A plurality of through-holes extending along a longitudinal direction of the respective articulation element is formed through each of the articulation elements. The through-holes are configured to convey a lubricant to a front side of an extreme distal articulation element of the series of articulation elements. The extreme distal articulation element has a deflector element.