A central vertical bore in the working head of a centrifuge rotor is sepd. from the tapered upper end of the internal drive shaft by a longitudinally slotted sleeve with an internal cavity of corresp. taper. The shaft end projecting above the bore is pressed towards the working head by engagement of an internally bevelled collar at the sleeve end with the inclined face of a ring held between discs projecting radially from the shaft end, with pressure derived from a screwed element.
