of the arrangements of fig1 to 6 is similarly applicable to the arrangements shown in fig7 a 7b 8 and 9 especially in the arrangements of fig7 and 8 there is a further advantage that as far as the spindle 2 is maintained in the neutral position both the first and second means for applying the axial force to the spindle to compensate for deviation thereof from the neutral position are inoperative and do not apply any axial force to the spindle thereby decreasing wear of the friction members and increasing the durability thereof with respect to a third embodiment shown in fig1 the restoring of the spindle 2 to the neutral position is adapted to be accomplished by first and second means both of which are not more in physical contact with the spindle in fig1 the spindle 2 is provided at the end away from the spinning rotor 1 with a disk like permanent magnet 10 a pair of permanent magnets 11 and 11 39 are spaced a predetermined distance and fixedly arranged on the opposite sides of the magnet 10 so that repulsive forces are produced between the magnets 10 and 11 11 39 thus it is understood that.