Originally Posted by
FBinNY
FWIW, I offered this as a mental exercise, and thought I adequately I qualified it as such.
In any case, the reference to "adequate tooling" implies making rather than buying. Also, it's not at all difficult to use an expander to generate enough traction for the purpose without damaging a CF steerer.
Stems have a hard time generating enough traction to keep aheadsets from working loose, and they have a considerable advantage in clamping than a tube that expands on the very end.
I guarantee you that an expander inserted and tightened enough to prevent the bearings working loose would cause the steerer to fail at the base of the expander, causing a horrendous accident. Carbon has very little crush strength, but we get away with clamping stems because that is compression and there's a plug. An unreinforced steerer being pushed out would yield almost immediately.
That's some extremely dangerous advice. It doesn't take much more than a few items from the hardware store make what you describe, so it wasn't a silly hypothetical that no one would do. Hopefully no one ever reads your post without reading the follow on, because your idea could get someone killed.
Please delete it.