Lifting Markov chains to speed up mixing

In a device for clamping a workpiece, such as an undressed casting, so that various surfaces of the workpiece can be mechanically worked, a platform having a support surface for the workpiece is pivotally mounted on a horizontal first axle located below the support surface. The first axle is pivotally mounted in a first cup-shaped housing which, in turn, is mounted for rotation about a vertically extending second axle. The first housing is pivotally supported within a second cup-shaped housing which is secured by swivel arms to a horizontal third axle located above and extending normally of the first axle. With the workpiece located on the support surface of the platform, the position of the surface to be worked is sensed to determine any deviations from a nominal position and by pivoting the platform about the three axles the surface can be precisely located for the working operation.