A workpiece holding assembly for a grinding machine, the assembly comprising: a magnetic chuck for holding a workpiece which has an outer circumferential surface and an inner circumferential surface located concentrically about a workpiece central axis; and a chuck drive for rotating the chuck about a chuck rotational axis during grinding, characterised in that the assembly includes first and second separate sets of workrests (26, 28, 30, 32) for engaging with the outer circumferential surface of an annular workpiece held by the chuck with a transverse side surface in engagement with the chuck, wherein the first and second sets of workrests are configurable as the workrests of at least one of the first and second sets of workrests are movable workrests which are movable relative to the chuck rotational axis independently of the workrests of the other set such that: when the outer circumferential surface of said workpiece is ground by a grinding wheel (42, 82) rotating in a grinding wheel rotation direction with the chuck rotating in a chuck rotation direction, the outer circumferential surface is only urged in contact with the first set (26, 28) of the first and second sets of workrests; and when an inner circumferential surface of said workpiece is ground by a grinding wheel (42,80) rotating in the grinding wheel rotation direction, with the direction of rotation of the chuck reversed relative to the chuck rotation direction during grinding of the outer circumferential surface, the outer circumferential surface is only urged in contact with the second set (30, 32) of the first and second sets of workrests. a magnetic chuck for holding a workpiece which has an outer circumferential surface and an inner circumferential surface located concentrically about a workpiece central axis; and a chuck drive for rotating the chuck about a chuck rotational axis during grinding, characterised in that the assembly includes first and second separate sets of workrests (26, 28, 30, 32) for engaging with the outer circumferential surface of an annular workpiece held by the chuck with a transverse side surface in engagement with the chuck, wherein the first and second sets of workrests are configurable as the workrests of at least one of the first and second sets of workrests are movable workrests which are movable relative to the chuck rotational axis independently of the workrests of the other set such that: when the outer circumferential surface of said workpiece is ground by a grinding wheel (42, 82) rotating in a grinding wheel rotation direction with the chuck rotating in a chuck rotation direction, the outer circumferential surface is only urged in contact with the first set (26, 28) of the first and second sets of workrests; and when an inner circumferential surface of said workpiece is ground by a grinding wheel (42,80) rotating in the grinding wheel rotation direction, with the direction of rotation of the chuck reversed relative to the chuck rotation direction during grinding of the outer circumferential surface, the outer circumferential surface is only urged in contact with the second set (30, 32) of the first and second sets of workrests. when the outer circumferential surface of said workpiece is ground by a grinding wheel (42, 82) rotating in a grinding wheel rotation direction with the chuck rotating in a chuck rotation direction, the outer circumferential surface is only urged in contact with the first set (26, 28) of the first and second sets of workrests; and when an inner circumferential surface of said workpiece is ground by a grinding wheel (42,80) rotating in the grinding wheel rotation direction, with the direction of rotation of the chuck reversed relative to the chuck rotation direction during grinding of the outer circumferential surface, the outer circumferential surface is only urged in contact with the second set (30, 32) of the first and second sets of workrests.