twist the sliver to obtain a spun yarn y fig1 illustrates the front bottom roller 5b and a structure for supporting the same the bottom rollers 5b formed of a metal are independent at every two spindles as previously noted and are interconnected by a later described coupling each roller 5b comprises draft portions 15 formed on both sides of a central portion 14 having a uniform thickness tapered portions 16 formed outside the draft portions and connections 17 of a small diameter formed at still outside end portions the draft portions 15 which are in pressure contact with the top roller 5a through the fiber bundle s have a diameter slightly larger than that of the central portion 14 and the connections 17 are of the smallest diameter the tapered portions 16 are each in a conical shape which connects the outer periphery of the draft portion 15 and that of the connection 17 smoothly to prevent the formation of a clear difference in height between both portions that is the outside diameter of the tapered portion decreases gradually from the draft portion 15 toward the connection 17 the front roller 5b is provided in plural numbers which are interconnected and fixed by means of a coupling 18 in an opposed state of the connections 17 numeral 19 denotes a bottom roller supporting block fixed onto a base 20 of the spinning machine the coupling 18 is housed in an axial bore 21 of the supporting block 19 and bearings 22 are provided between the connections 17 on both sides of the coupling 18 and the supporting block 19 whereby the bottom roller 5b is supported rotatably numeral 23 denotes a collar for preventing the entry of dust etc and numeral 24 denotes a bolt for fixing.