Positioning base the choice of gear shaft on the surface of the primary processing purchase, to a big extent depends on the selection of locating datum structure characteristics and the main shaft of the shaft parts on the surface of the main location accuracy requirement is set the axis as benchmark may be the ideal not just make sure that benchmark is planetary gearbox unified, and make the locating datum and the design datum coincidence outside circle intended for crude benchmark more commonly, upon both sides of a sharpened hole for great benchmark concrete also notice the following points: (1) when the choice between machined surface area when the position accuracy of high, best carried out in a clamping surface area processing (2) for rough machining or when two end center holes (such as spindle cone hole) can’t 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 center hole can be utilized as positioning reference