threshold values significantly this type of adjustment is necessary every time the yarn size of the yarn to be spun is changed the spinning location 10 39 illustrated in fig2 is similar to that shown in fig1 the drawing machine 11 in this embodiment has three roller pairs 40 41 and 14 which draw the two fiber strands 17 17 39 therethrough in spaced parallel relation these two fiber strands 17 17 39 which are not illustrated separately in fig2 since it is a side view merge at a common joining point 9 after leaving the final roller pair 14 this joining point 19 is formed between the final roller pair 14 and the yarn guide 25 which is arranged coaxially above the spindle 26 the two fiber strands 22 22 39 leaving the final roller pair 14 as individual fiber strands are twisted together to form the yarn 23 which is wound on the spindle 26 a suction tube 42 of an aspiration device 43 is disposed a short distance below the final roller pair 14 the aspiration device 43 includes a main suction chamber or channel which extends along the entire length of the machine from which the various suction tubes 42 branch off at each spinning location each suction tube 42 has a slot like.