Originally Posted by
soyabean
I don't think the OP realizes that there are dozens of types of bottom brackets, and the one in diagram is a popular sealed unit, which may not apply to the OP.
"middle cylinder is missing" means it isn't a sealed unit, and just a crown race bearing type found on most big box store bikes.
Seat tube "corrosion" isn't an issue and safe to leave as-is. A well lubed seatpost is all it takes.
The OP did all this for nothing, and sure caused more damage by inadvertently honing out the seat tube to a possibly larger diameter.
This is why exists Local Bike Shops.
They are there to help.
the term "crown race" refers only to a part of a Headset.
and many cup and cone BB assemblies come with a removable plastic tube to help prevent garbage and water from easily entering the BB bearings... whether it's "missing" or not has yet to be determined.
To Cemark... nice job cleaning up the bike's tubes ! there are products meant to coat the insides of frame tubes to limit further rusting... here's an article on the process.. there are others, i'm certain.
https://surlybikes.com/info_hole/spe...ur_steel_frame
If the Rust has popped through the tubes in ANY AREA, the frame is not even close to "safe" and don't waste another minute on it, ok? just find another frame or project with less rust..
so far, it appears the frame is worth saving.. wha brand and model?