to that defined by a thirty inch column of water the magnitude of this vacuum can be varied by varying the output of the vacuum pump so as to vary the velocity of the air passing through the conduits 52 by varying the velocity of air passing through the conduits differing quantities of fiber can be advanced to the break spinning means and the density and thickness of the yarn produced by each spinning means can be varied each break spinning means is provided with a suitable bypassing means such as the bypassing tube 70 leading from the conduit adjacent the entry nozzle around the housing 58 to the vacuum tube 64 discharging from the housing 58 the bypassing tube 70 is employed to divert the stream of individual fibers otherwise entering the spinner around the housing 58 in the event that an end comes down to the spinning means should this occur the fibers will be diverted around the housing of the spinning means and yet the other spinning means associated with the single opening roll 40 can continue to operate additionally fibers which would otherwise be conducted into the interior of the spinner are diverted around the chamber thereof so that the spinning means having the broken length of fibers can be rethreaded quickly and placed back in operation without cleaning thus operations can continue essentially uninterrupted but for the particular break spinner having the broken length of fibers the individual fibers passing to a spinning means are diverted through the bypassing tube 70 by the action of valves 72 and 73 located at either end of the bypassing tube in the course of normal operation the valves 72 assume the posture shown in phantom in the drawing the bypassing tube is thus closed to fibers entering the.