Rigid out-covered clamping device of vertical fine boring machine

The invention discloses a rigid out-covered clamping device of a vertical fine boring machine, comprising a clamping canister provided with a connection seat, wherein the middle-lower part of the outer wall of the clamping canister is provided with a fixed ring; the fixed ring is matched with the inner wall of a sleeve through an O-shaped seal ring, wherein the length of the sleeve is less than that of the clamping canister, an upper flange plate and a lower flange plate are fixed on the sleeve; an upper vent hole and a lower vent hole are arranged on the sleeve, the inner end faces of the upper flange plate and the lower flange plate are both matched with the outer wall of the clamping canister through the O-shaped seal ring; an upper locating ring and a lower locating ring are arranged on the inner wall of the clamping canister; a pressing ring for fixing the upper end surface of a workpiece is fixed on the upper locating ring; a support ring is fixed on the outer wall of the clamping canister close to the top end; three brackets are evenly arranged on the support ring and are all movably connected with a pressing plate through a shaft; one end of the pressing plate corresponds to the upper end surface of the pressing ring, and the other end corresponds to a jack-prop fixed on the flange plate on the sleeve. The clamping device solves the precision problems of large conicity, poor depth of parallelism, horn mouth occurrence at two calibers and the like during boring, which are caused by that the length of the inner hole of a large-size workpiece is longer, thereby improving the replaceability and installation precision of the clamp and the quality of products.