Abstract: The present invention relates to an indexing mechanism for stepwise advancing a workpiece relative to a cutting tool of a machine tool, to enable slices or wafers of predetermined thickness to be cut from the workpiece. The indexing mechanism comprises first and second slide blocks slidable in a slideway in a slide block carrier of the machine tool. The first block carries the workpiece and the second block carries a double-acting index actuator which interconnects the two blocks and is operable to displace the blocks alternately toward and away from each other, the extent of said displacement determining the indexing stroke of the mechanism. The index actuator is provided with an adjustable end stop for adjusting the indexing stroke.