Outer-diameter-adjustable forging and milling tool

The invention relates to a downhole tool for oil and gas field well repair, in particular to an outer-diameter-adjustable forging and milling tool capable of being used for grinding and milling sleeves with different outer diameters. The outer-diameter-adjustable forging and milling tool comprises an upper threaded joint, a main body shell, position limiting screws, a cutter position limiting block fastening screw, a position limiting circular ring, a connecting joint, a centralizing guide shoe, cutters, a cutter position limiting block, a flow dividing disc, an upper piston rod, a reset spring, a piston rod stop block, a cutter positioning screw, a piston rod joint, a flow guide joint, an incomplete gear and the like, wherein the upper end of the upper threaded joint is fixedly connectedwith the lower end of a workover string through screw threads; three rows and six columns of position limiting screws are uniformly arranged in the middle of the body shell in the circumferential direction; and the six cutter