Positioning base the choice of gear shaft upon the surface of the main processing purchase, to a big extent depends on selecting locating datum structure characteristics and the primary shaft of the shaft parts upon the surface of the primary location accuracy necessity is set the axis as planetary gearbox benchmark is the ideal not just make sure that benchmark is unified, and make the locating datum and the look datum coincidence outdoors circle to get crude benchmark more commonly, upon both sides of a sharpened hole for good benchmark concrete also take note the following points: (1) when the choice between machined surface when the positioning accuracy of high, greatest completed in a clamping surface area processing (2) for tough machining or when two end center holes (such as spindle cone hole) can’t be used designed for positioning, to improve the stiffness of the process program during workpiece processing, just cylindrical surface area or cylindrical surface and one end middle hole can be used as positioning reference