Tensioner

The utility model discloses a tensioner which comprises a disc, and a jacking device used for making contact with the inner wall of a machined part and fixing the machined part is arranged on the disc. The driving device is used for driving the jacking device to move radially along the disc, and the bolt is in threaded connection with the cone frustum, so that threads are convenient to replace after being abraded; the expansion angle is broad bean-shaped, two high points of the expansion angle are contacted with the inner wall of the product, the contact area is large after two points are contacted, and product deformation in the expansion process is prevented. The expansion angle is hinged with the supporting rod, so that the flexibility is ensured, and the self-adjustment and the automatic adjustment of a matching surface are facilitated under the condition that the contact surface of a product is elliptical or uneven; the circle center of the combination area is automatically adjusted and aligned, the devi