not shown on its portion which protrudes out of the intermediate plate 22 a bearing body 25 can be clamped to the intermediate plate 22 by means of the tightening nut wherein the bearing body 25 is slidably guided on the intermediate plate 22 in the direction of double arrow 26 and thus perpendicularly of the base rail 1 the length of this displacement is limited by an oblong hole 27 in which a bearing body 25 has been placed and through which the screw not shown projects the bearing body 25 includes a bore 28 which together with an insertable nail or the like forms the pivot axis 29 for the base rail 1 this nail can be driven into the workpiece to be processed so that the pivot axis 29 is stationary and a movement of the processing apparatus on a precisely given circular line is possible the adjustment of the bearing body 25 on the intermediate plate 22 makes it possible to adjust the pivot axis 29 precisely at that distance from the base rail 1 which is equal to the distance from the center of the processing tool of the processing apparatus to the base rail 1 as a result it is always ensured that the movement of the processing tool of the processing apparatus takes place on the circular line which has a center point coinciding with the pivot axis 29 in a saw blade like tool this ensures that the processing tool does not get jammed the distance of the marking 10 between the processing tool and the lower end of the base rail 1 shown in the drawing.