The slivers from the first drawing frame are now subjected to a further process of doubling and drafting in a very similar machine termed the second drawing frame. The pins in the gills for this frame are rather finer and more closely set than those in the first drawing frame, but otherwise the active parts of the machines, and the operations conducted therein, are practically identical, and therefore need no further description. It should be mentioned, however, that there are different types of drawing frames, and their designation is invariably due to the particular manner in which the fallers are operated while traversing the closed circuit. The names of other drawing frames appear below. Spiral or screw gill; Open link chain; Rotary; Ring Carrier Circular. For the preparation of slivers for some classes of yarn it is considered desirable to extend the drawing and doubling operation in a third drawing frame; as a rule, however, two frames are considered sufficient for most classes of ordinary yarn. CHAPTER IX. THE ROVING FRAME The process of doubling ends with the last drawing frame, but there still remains a process by means of which the drafting of the slivers and the parallelization of the fibres are continued. And, in addition to these important functions, two other equally important operations are conducted simultaneously, viz., that of imparting to the drawn out sliver a slight twist to form what is known as a "rove" or roving, and that of winding the rove on to a large rove bobbin ready for the actual spinning frame. The machine in which this multiple process is performed is termed a "roving frame." Such machines are made in various sizes, and with different types of faller mechanism, but each machine is provided for the manipulation of two rows of bobbins, and, of course, with two rows of spindles and flyers. These two rows of spindles, flyers, and rove bobbin supports are shown clearly in Fig. 18, which represents a spiral roving frame made by Messrs. Douglas Fraser & Sons, Ltd., Arbroath. Each circular bobbin support is provided with pins rising from the upper face of the disc, and these pins serve to enter holes in the flange of the bobbin and thus to drive the bobbin. The discs or bobbin supports are situated in holes in the "lifter rail" or "builder rail" or simply the "builder"; the vertical spindles pass through the centre of the discs, each spindle being provided with a "flyer," and finally a number of plates rest upon the tops of the spindles. [Illustration: FIG. 18 ROVING FRAME _By Permission of Messrs. Douglas Fraser & Sons, Ltd_.]