The diagram in Fig. 7 shows the relative displacements of all these parts, as well as those of the scraper guide, C. The diameter to be obtained is determined beforehand by the two contact screws, P.
The whole thus regulated, the bar of iron, still very hot, coming from the ordinary rollers, is straightened up, if need be, by a few blows of a hammer, so that it may roll forward over the pavement, N, between the rounding cylinders, A A; these being held apart sufficiently to allow of its easy introduction. Next, a few revolutions of the winches that control the screws suffice to lower the upper cylinder to the exact position limited by the contact screws, P, and the bar is rolled between the two cylinder tables with a constant velocity in the generatrices. As a consequence, the number of revolutions made is so much the greater in proportion as the diameter of the shaft is smaller with respect to that of the cylinders.
It should be remarked that the bar, during its rotation under pressure, is held by the guide, C, so that its diagrammatic axis (Fig. 7) exceeds the line, A A, joining the centers of the cylinders just enough to prevent its escape to the opposite, and so that the pressure upon the said guide (which performs the role of scraper) is merely sufficient to detach the scales which form during the operation.
Under such conditions, and at a velocity of 30 revolutions per minute in the two cylinders, it will take but a fraction of a minute to finish a bar the length of the table, that is to say, 1.5 meters. Then, by loosening the upper cylinder, the bar may be easily shoved along in one direction or the other, so as to continue the finishing operation on successive lengths. This moving of the bar forward is further facilitated by the aid of a clamp with rollers and a movable socket, V (Figs. 8 and 9). For large diameters (150 millimeters and beyond) traction is employed by the aid of two small windlasses placed opposite each other, and at a distance apart twice the greatest length of the bars to be finished. The chains of these windlasses are attached to the extremities by clamps that lock by the pulling exerted.
The details of the arrangement of the saws (Figs. 5 and 6) show that to make a section of the ends or of any other part of the bar, it is only necessary to lower the lever of one them. By reason of the contrary rotation of the bar, the effective stress on the lever will be very moderate, while the cut produced will be a clean and quickly performed one. It should be remarked that, as a consequence of the cone on the projecting extremity of the cylinder journals (Fig. 5), and on the rollers that control the saws, it is only necessary to move the lever to the right or left in order to stop the motion of each of the saws. These latter, to prevent all possibility of accident, are inclosed within semicircular guards. Finally, the controlling rollers are made of a material which is quite elastic (compressed cardboard, for example), so that they may roll smoothly and adhere well.