Abstract: A mechanism for rotating a machine element and in particular for rotating a mandrel which holds a workpiecein a machine comprises a first frame member having a substantially linear road surface. A machine element is rotatably secured to a carrier on an axis extending transverse to the road surface. The machine element includes a wheel member having a substantially circular wheel surface adapted to engage the road surface, and may include a mandrel adapted to hold a workpiece. A first drive mechanism is operable for moving the carrier and the first frame member relatively together for engagement of the wheel surface with the road surface, and for moving or at least permitting movement of the carrier and the first frame member relatively apart for disengagement of the wheel surface from the road surface. A second drive mechanism is operable to produce relative movement of the carrier parallel to the road surface.