Fine-tuning indexable eccentric composite boring cutter

The utility model provides a fine-tuning indexable eccentric composite boring cutter which comprises a cutter handle and a cutter bar which are integrally connected, the cutter bar is eccentrically arranged on the cutter handle and meets the following condition: D = R1 + R2, D is the diameter of the cutter bar, R1 is the minimum radius from the cutter bar to a rotating shaft, and R2 is the maximum radius from the cutter bar to the rotating shaft; a rough boring blade and a fine boring blade are sequentially arranged on the maximum radius side of the cutter bar from the front end to the rear end, R3 is larger than R2 and smaller than R4, R4-R3 = R0, R3 is the rotating radius of the rough boring blade, R4 is the rotating radius of the fine boring blade, and R0 is the reserved size of the hole diameter from rough boring to fine boring and the axial distance between the rough boring blade and the fine boring blade. According to the eccentric boring cutter, machining of an inner hole of a stepped hole with the low