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@gbj_tester
Not really, it's just a normal bearing press fit, the kind of thing that passes without comment in hubs and normal BBs. The bore is 42mm with tolerance of -0.015 to -0.040, which is 25μm between go and no-go. Colloquially speaking, high precision is working to ±1μm, and fairly ordinary CNC shops routinely work to ±10μm. At best, you might say that BB30 requires precise tolerance on the bore of the BB shell. There is no specified tolerance on the concentricity or axial alignment of the two bearing seats, beyond an instruction to cut both seats with one cut.