Abstract: A mounting for a load rotating or oscillating about a vertical axis comprises a stationary annular support member centered on that axis and provided with inner and outer peripheral guide tracks engaged by two rotatable annular carrier members, either the stationary member or the rotatable members being split along a horizontal plane for positive interfitting. A load-carrying platform overlying the three coaxial members is separated from the stationary member and from one of the carrier members while being secured to the other carrier member through the intermediary of an interposed spacer for rotary entrainment thereof. The spacer, in the form of a multiplicity of ring segments, can be transferred to the previously idle rotatable member upon excessive wear of the guide track associated with the carrier member previously entrained.