Size-adjustable centering tool

The invention relates to a size-adjustable centering tool. The tool comprises at least: a support shaft bracket, a drive unit which is rotatably arranged coaxially to the support shaft bracket outside a hub of the support shaft bracket, and a positioning unit which is connected in a meshing manner to the drive unit. When the drive unit is subjected to a force and rotates, the positioning unit is driven by the rotating energy of the drive unit to move, so that a plurality of moving assemblies in the positioning unit move equidistantly in the radiation direction with the axis of the support shaft bracket as the center, and under the condition that the plurality of moving assemblies of the positioning unit move equidistantly in the radiation direction and make contact with the end of a positioning object, the moving assemblies are limited by the end of the positioning object so that the axis of the shaft hole of the support shaft bracket can coincide with the axis of the positioning object. According to the cent