Abstract: In a positioning and turning apparatus for the machining of heavy workpieces, the problem of inaccuracies caused by bearing play and drive stresses and standing in the way of a sensitive and accurate setting and thus the use of numerical controls and controlled positions is eliminated by using ring bearings with a large cross-section which can be used as compact building units and connected to large drive-geared wheels, resulting in a definite gain as regards rigidity, freedom from play and precision. With a cross carrier on the carrier of a positioning and turning apparatus, the workpiece is translatorily movable in addition to its rotatability around two axes, being adjustable particularly with respect to the axis of rotation so that an optional radius can be set in the case of curved machining like, for example, curved welding seams.

Abstract: To enable heavy workpieces to be orientated into any desired position without re-clamping, more particularly for welding seams horizontally from above, as is most favorable, a clamping plate or table (3) is pivoted for unrestricted rotation about an axis (5) at the free end of a cantilever arm (2) supported from a stand (1) for rotation about a horizontal axis (13) by flange elements (14, 15) which are adjustable with respect to one another in two directions at right angles to balance a workpiece and the cantilever, table assembly with reference to the axis (13). Electric motor drives (7 and 12) controlled by limit switches may be used to selectively rotate the table and the cantilever arm to bring a workpiece into any desired orientation. A construction in which the cantilever (2) is replaced by a beam extending two end frames like the stand (1) is also described.