PURPOSE: To quickly exchange only a sleeve by setting the sleeve loadably/ unloadably on an arbor by adjusting the supply/discharge of pressure oil in hydraulic chambers provided on both sides of each tapered sleeve.

CONSTITUTION: The pressure oil is supplied from a port 30 to the hydraulic chamber 42 via an oil passage 42a by using a hydraulic system, for example. a hand pump, etc., and simultaneously, the pressure oil in the hydraulic chambers 41L, 41R are discharged to a tank. In such a state, upper sleeves 11 moved outward in the right and left directions from the center parts of the tapered sleeves 13R, 13L and the tapered sleeves 13R, 13L are released from a wedge state and the upper sleeves 11 become loose. In such a case, after the upper sleeves 11 with mortal diameter due to a flaw or nonuniform wear are extracted from an upper arbor 12, they are exchanged with ground new sleeves 11. When the new sleeve 11 is loaded on the desired position of the arbor 12, the pressure oil can be supplied to the hydraulic chambers 41R, 41L via the oil passage 41a by supplying the pressure oil to the port 33 by the hand pump, etc.