Scribing device and scribing method for inner conical surface of part

According to the scribing device and method for the inner conical surface of the part, the scribing device comprises a fixture used for being erected on an opening of the conical part, the left side face of the fixture is a positioning face C and used for abutting against a positioning face A of the conical part, three positioning pins are arranged on the fixture and distributed in a triangular shape, and the three positioning pins are arranged on the fixture; the outer cylindrical surface of the positioning pin is used for abutting against the inner wall surface of the opening part of the conical part; the rotating shaft is rotatably mounted in the center of the fixture; and the floating marking knife is mounted at the end, extending into the conical part, of the rotating shaft. By the adoption of the marking device, after the floating marking knife is installed on the rotating shaft, the rotating shaft is installed on the fixture, when the inner conical surface of the conical part is marked, the fixture is