Pivotal structure

The utility model relates to a pivotal structure, comprising a sheath joint component and a pivot joint component. The sheath joint is provided with a hollow sleeve barrel, at least one barrel groove is transversally opened on the circumference of the sleeve barrel, and at least one flat cut surface is formed on the inner wall; a connecting part is extended from one side of the sleeve barrel, and at least one joint hole is opened on the surface of the connecting part. An axis column whose diameter is slightly longer than the inner diameter of the pivot joint is protruded from the pivot joint component corresponding to the opening of the sleeve barrel, and at least a milling surface is formed on the circumference of the axis column; the axis column is inserted into the sleeve barrel, and is adjoined with a pivot joint part on the surface of which a pivot hole is provided. The distance difference from the milling face of the axis column to the opposite circumference is shorter than the diameter; by the distance difference, when the milling face is contacted with the flat cut surface, the sleeve barrel is retracted inward for the distance difference, and a lateral thrust force is formed, to make that the milling face can move along the flat cut surface to form automatic recombination.