A roll forming machine is provided having a plurality of sets of rotatable opposed drive rollers having parallel axes with each set of drive rollers including at least one forming edge in roll forming machine. Each set of drive rollers in roll forming machine also includes at least one rotatable forming roller opposite a forming edge and having its axis in a plane defined by the parallel axes of the set of drive rollers in roll forming machine. The angle between the axes of the drive rollers and forming roller of each set is increased incrementally in successive sets. The contact surface of the drive roller defines a right circular cylindrical surface. The contact surface of the forming roller defines a frusto-conical surface and preferably a right circular cylindrical surface.