This work is done in a reeling machine, the principle of which is shown in Fig. 69.

Fig. 69. - Making Seamless Tubes. Tube Reeling Machine.

Supposing the axis of the tube to lie in the plane of the page, the axis of the upper roll is inclined downward toward the right, and that of the lower roll is inclined downward toward the left. The revolutions of the rolls inclined in this way not only revolve the tube, but push it forward over the mandrel M. The mandrel is supported by its bar R, and is free to revolve with the tube. This operation may change the tube diameter somewhat.