Abstract: A single electric motor is employed to drive two, separate backup roll supporting shafts which are mounted to rotate about a common horizontal axis. A first, solid, cylindrical backup roll of relatively small diameter (less than 11/2") is secured to one end of one of said shafts for rotation beneath a first grooving roll, and a second, relatively larger diameter backup roll (greater than 11/2" and less than 2"), which is annular in configuration, is secured coaxially to one end of the other shaft for rotation thereby beneath a second grooving roll. Each grooving roll is mounted for vertical reciprocation by springs and by a hydraulic ram supplied by fluid from a separate hand pump. Means is also provided for adjustably limiting the descent of each backup roll.