Flightsafety, regarding 'grinding" of seals, blades, etc. GE were not kidding. This is a recognised process called "tip grinding" conducted on a massive thing called ...a tip grinder.
You put the built up shaft assembly into the grinder, spin it up to 2000-3000 rpm and then apply the grinding wheel to the tips of the blades, that way you are setting tip clearances under something closer to the dynamic loads and you can thus set tighter tolerances elsewhere.