main housing has two vertically adjoining horizontally transversally oriented cylindrical sockets 130 132 formed therein the lower one 130 mounts a lower shaft 134 and its bearings 136 at the laterally outer side of the main housing a hydraulic motor 138 is drivingly connected to the lower shaft 134 at the laterally inner side of the main housing a lower driving roll 135 is secured on the lower shaft 134 the upper socket 132 mounts an eccentric bearing housing 140 having a band of gear teeth 142 provided angularly of its exterior in the eccentrically located socket 144 provided in the housing 140 an upper shaft 146 and its bearings 148 are journalled at the laterally outer side of the main housing a hydraulic motor 150 is drivingly connected to the upper shaft 146 at the laterally inner side of the main housing an upper driving roll 152 is secured on the upper shaft 146 the upper and lower drive rolls have respective radially outer peripheral surfaces of substantially semicircular cross sectional profile and are polished so that the two surfaces may drivingly engage between them a major portion as much as substantially all of the surface of a tube being fed in the nip thereof without scuffing the surface of the tube the main housing 120 is seen to further include a longitudinally oriented horizontal socket 154 which intersects the upper socket 132 in the socket 154 there.