Precision boring consists of re-boring an existing hole to micrometric accuracy, typically to restore a degraded dimensional tolerance, step up to the next oversize after cold working, or create a very high precision mating surface. Spot facing completes the operation by ensuring the flange's flatness and perpendicularity.
On aircraft structures these operations are performed on-site with portable high-precision tooling (Rotabroach, Recoules, OEM-specific tools) operated by qualified structures technicians. Dimensional traceability (dial indicators, bore gauges) is mandatory for OEM compliance.