Originally Posted by
JohnDThompson
The "brassy" looking material is copper, which is used as a base layer under chrome plating because chrome doesn't adhere well to steel. The middle part where the balls run is the underlying steel. The balls have worn through both the chrome and the copper and are now bearing directly on the steel.
I dunno, don't see it. What I usually see on my headset rebuilds is a distinct and narrow roughish track in the race area, where the balls progress one after the other. Maybe it's my monitor, but that's not what I see. If the chrome and copper layer are worn through, I'd expect to see a track, with a gray center, a copper border, and the chrome outside. I just see chrome all across the race.
The radius of the bearing ball has to be less than that of the race surface, to promote point contact of the ball, but there is to my eye no visible track. Could you be saying that the balls have kind of lapped their way completely into the race?