Positioning base the decision of gear shaft upon the surface of the primary planetary gearbox processing purchase, to a sizable extent depends on the selection of locating datum structure characteristics and the primary shaft of the shaft parts on the surface of the main location accuracy necessity is decided the axis since benchmark is the ideal not just ensure that benchmark is unified, and make the locating datum and the look datum coincidence outdoors circle meant for crude benchmark more commonly, upon both sides of a sharp hole for great benchmark concrete also note the following points: (1) when the choice between machined surface when the positioning accuracy of high, greatest done in a clamping surface processing (2) for rough machining or when two end middle holes (such as for example spindle cone hole) cannot be used intended for positioning, to enhance the stiffness of the procedure system during workpiece processing, just cylindrical surface or cylindrical surface area and one end middle hole can be utilized as positioning reference