Abstract: The invention pertains to hone stone apparatus utilizing radially movable stone assemblies located in a rotating or oscillating head and radially movable through openings defined in the head for engagement with the workpiece. The stone assemblies include an abrasive stone partially embedded within a synthetic plastic body and the end regions of the body are slightly oversized with respect to the head opening configuration and the body end regions are slotted to permit compression wherein a firm frictional engagement exists between the stone assembly and the head for retaining the stone assembly within its head opening.