Originally Posted by bulgie

If the crown is chrome plated, then I wouldn't use a Campy crown race cutter on it (or any other brand that I cared about). If there's a paint buildup over the chrome, I'd use abrasive cloth or a file to remove it — and not one of my good files either. Chrome dulls cutters, like instantly.

From your dimension, it sounds like the cylindrical part of the seat is close enough. Maybe the flat part at the top of the crown doesn't lie in a plane that's perpendicular to the steering axis? If so and if it's plated, than that's a major screwup. You don't plate a crown until the headset seat is trued up.

If there's chrome and one or both surfaces do need truing up, then doing it on a lathe with a single-point tool is recommended. That's an easy job for most anyone with a lathe, except for mini-lathes whose spindle bore is less than 1" so the steerer won't fit down the bore.

I somewhat doubt yours needs cutting though. Pics are a must.