Originally Posted by
FBinNY
Because, unlike the raw steel of a seat tube, steel headsets tend to be chrome plated.
Besides, the differences in engaged surfaces, ie 10-15mm vs 60+mm for seatposts and the ease of knocking out from the bottom argue against the likelihood of sawing to remove.
I have no competing theory except that it was either intentional or accidental.
Early on, I offered a fix. That's how I deal with stuff like this. I focus on solving the problem, and leave fanciful theories on who might have done what to others.
Sometimes, I do explore questions of how stuff goes wrong, either out of intellectual curiosity, or if I think there's a benefit in knowing.
Then you dont understand galvanic corrosion. It is preferential corrosion, so it only happens on the aluminum side, forming aluminum oxide. The steel, carbon or Ti does not corrode. So unless you believe chrome is an insulator, the steel is going to be the cathode and the aluminum the anode.
Whoever cut this headtube screwed up. I have no idea how stuck the cup really was and if the mechanic's judgement to cut it was reasonable. I just recognize the kind of tool marks that kind of cut leaves if you don't pay attention.