| 摘要 |
PURPOSE:To hold a center pin with high accuracy in spite of the clearance between a holding body and the center pin and prevent the lowering of accuracy caused by change with time by loosely fitting the center pin into the holding body having a pressure-oil storage groove and holding the center pin by means of the elastic deformation of the holding body. CONSTITUTION:As a workpiece 11 is fed, a draw screw 8 is drawn and a high pressure oil is fed into a storage groove 13 from a hydraulic pump prior to the completion of holding by a jaw 7. A holding body 12 is fitted into a holder 3 and surrounded by the whole periphery of a storage groove 13 on the inner peripheral face 14a of a fitting portion 14 forming a closed chamber, while the holder 3 is firmly formed in a body with a chuck body 2. Hence, the pressure of oil acts toward the axis of the holding body 12 and elastically deforms the bottom portion having a thin wall thickness (t), interposingly holding a loosely fitted center pin 4 and absorbing the clearance to carry out center adjustment for making the chuck body 2 agree with the axis of the center pin 4, thereby holding the workpiece 11 with high accuracy. |
