Positioning base the decision of gear shaft on the surface of the primary processing order, to a big extent depends on the selection of locating datum structure features and the main shaft of the shaft parts on the surface of the primary location accuracy requirement is decided the axis since planetary gearbox benchmark may be the ideal not just make sure that benchmark is unified, and make the locating datum and the design datum coincidence outside circle pertaining to crude benchmark more commonly, upon both sides of a sharp hole for good benchmark concrete also take note the following points: (1) when the decision between machined surface area when the positioning accuracy of high, best done in a clamping surface area processing (2) for rough machining or when two end center holes (such as for example spindle cone hole) cannot be used meant for positioning, to improve the stiffness of the process system during workpiece processing, just cylindrical surface area or cylindrical surface and one end middle hole can be used as positioning reference