Abstract: A dressing device for shaping grinding wheels for use in manufacture of gear wheels and the like, comprises an arm (4) supported intermediate its ends by a spherical bearing (5,9) for free angular movement about a fixed point (P) on the arm axis and for rotation about the axis. The working element (2) e.g. a diamond, is carried on the forward end of the arm and a control mechanism adapted for automatic electronic control is coupled to the rear end of the arm through a gimble (6,7). The control mechanism includes a pair of slide tables (17,20) having respective motors (18,21) for movement in mutually perpendicular directions (x,y) and a third motor coupled to a gear (24) fast with the arm for rotating the arm.