Backoff reducing boring milling cutter

An inverted reducing boring milling cutter comprises a special cutter blade and a radial movable cutter holder, and the cutter blade is mounted on the cutter holder. The supporting tool apron is fixed to the tool rest T-shaped groove. The pitched roof in the middle of the tool rest is in contact with the tool apron, axial movement of the pitched roof can drive the tool apron to move radially, and a reset spring is installed at the bottom of the pitched roof and can be matched with reciprocating movement of the pitched roof. A fixed electromagnet is installed in the tool rest and connected with the pitched roof, and a conductive slip ring is installed outside the tool rest, so that the tool rest can still provide electric energy for the electromagnet in the tool rest under the condition of circumferential rotation. A flange plate is arranged at the lower end of the tool rest and can be installed on a motor and fixed tool machining equipment. When the cutter is used for machining, the electromagnet is powered o