Originally Posted by
krome
I haven't done frame repair, but I've done braze and weld repair. Someone who knows how to braze will add material (braze) to the headset tube. This will decrease the inner diameter, done right. After the repair, some metal (braze) will have to be removed (with a reamer) to fit the new cups anyway. If properly done, they will press fit again. Key here is to determine the root cause. Accident? Bad material? Bad cup install? Improper size cups? Determining the cause will influence the remedy. Otherwise I'm in full agreement with what you said.
I'm not going to say that brazing the crack is the proper way to repair this frame, but I don't see a crack braze repair as being incompatible with press fitting new cups. Brazing adds material. If it were my bike, I'd most likely braze an additional piece of steel across the crack, to beef up the area. I wouldn't presume to make it look like it was before the crack, just make it safe to ride. It will leave a "scar" if you will.
I was thinking the polished parts were stainless. Being chrome will complicate things (cosmetically).
Adding material isn't the point. The added material would be in the wrong direction. The crack has changed the diameter of the headtube slightly and adding material to fill the gap will only fill the gap. It does nothing to return the diameter of the headtube to it's original diameter. The amount that the diameter has changed may be small but it has still changed. That's going to have an effect on how the headset fits and functions.