are provided for each row of tubes 24a b c in an alternative clamping means the beams 32a b 34a b are biassed apart by compression springs and a pneumatic ram acts on beam 32a to overcome the spring force and clamp the beams together upon release of the pneumatic ram the springs urge the beams apart to a condition similar to that of fig2 thus the tubes 24a b c are mounted in cantilever with their axes substantially parallel to the axis a of the base 12 in this embodiment the tubes 24a b c are almost as long as the base so that only a small gap exists between the free ends 42 of the tubes and the carrying means 18 in its position of rest as shown in fig1 it will be understood that the machine base could be long enough to accommodate tubes of a length desired to be used e g 6 metres or more however it would alternatively be possible to support very long tubes at their mid point i e to fit a sleeve around the middle of the tube which sleeve could then be clamped as above and then successively fin the separate halves of the tubes from each respective end following the finning of such a tube.