Originally Posted by
Al1943
If it takes a lot of force to hammer the race on don't do that! There is a special tool for facing the crown sleeve. If it just needs a little help I would try some medium grit (220 - 240) wet automotive sand paper.
The OP describes a steerer with a crown seat diameter extending up about an inch. This then is not a classic brazed steel fork with a machinable crown seat as part of the crown, but a
bulge formed steerer either of steel or carbon (he doesn't specify).
Neither of these are designed to be milled, and should come from the factory within tolerance ---- 5/100ths of a millimeter over the nominal. If it isn't that or close - plus or minus a few 100ths of a millimeter, something is wrong, and his best course of action is to either return the fork, or consult someone familiar with the job.
There's no harm in sanding off a few 100ths of a mm on a steel bulge formed steerer. but it shouldn't be necessary, and IME very rarely is. If in doubt, the first step would be to measure. Remember it's always possible to remove material, but never possible to add back.