Fixture

The invention provides a fixture. The fixture comprises a clamping mechanism, a force applying sleeve and a columnar body assembling the clamping mechanism and the force applying sleeve; the clampingmechanism is provided with two mutually hinged clamping bodies, and at least one clamping body is provided with a rolling part; the columnar body is provided with a first through hole running throughthe side wall of the columnar body in the axial direction, the clamping mechanism is contained in the first through hole, and the clamping mechanism is assembled on the columnar body through a rotating shaft at the hinged portion; a second through hole is formed in the columnar body in the axial direction, and the second through hole is communicated with the first through hole; an arc-shaped surface cooperating with the rolling part is arranged on the inner wall of the force applying sleeve which sleeves the columnar body, when the force applying sleeve moves along the columnar body, the forceapplying sleeve compresses