Positioning base the planetary gearbox decision of gear shaft upon the surface of the main processing order, to a big extent depends on the selection of locating datum structure features and the main shaft of the shaft parts upon the surface of the primary location accuracy requirement is decided the axis because benchmark is the ideal not only make sure that benchmark is unified, and make the locating datum and the look datum coincidence outside circle to get crude benchmark additionally, upon both sides of a razor-sharp hole for good benchmark concrete also take note the following points: (1) when the decision between machined surface when the positioning accuracy of high, best completed in a clamping surface 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 procedure program during workpiece processing, just cylindrical surface area or cylindrical surface and one end middle hole can be utilized as positioning reference