Caustic soda on stuck BB

I don't think it will get you far. It is used to dissolve aluminium seatposts out. But bottom brackets are steel...
 
The cups are alluminium though, otherwise this one ain't coming out
 
Re:

Depends what it is, but go for getting the axle out first then just cut through the the threads in places and crimp it in.

It may mean dismantling the bearings cGes.
 
Exactly what I thought !
Am I right in thinking it's the bearings that hold the axLe in?
 
Yes, well normally.

With shimano, get the shields and covers off, then remove the plastic cage, bearings will be free, Do the same at both side , move bearing to one side, then hit the axle into the free space. Pull axle out.

With other more traditional cartridge bearings on an axle, then just get a screwdriver and try your best to destroy the cages and pop the bearings out.
One done axle should hammer out (easier than I say as it took me ages to get one apart OFF the bike, need for a bearing replacement (FSA Ultimax))

Cut the cups a bit then tap the outer bearing race out the way, continue.

Bodge and hack as you go along.

Works for me anyway. Hardest I did was a Shimano on an Orange Alu-O. just be careful when you get to thread depth, stop and start another and do it in parts (the cup will be so thin it'll just snap, saving the frame threads....
 
Re:

managed to get a stuck xt bb out of a steel rocky last month. Caustic soda soak over a few days. worked a treat. be careful though its dnagerous stuff. all done outside, glasses gloves used. dissolved the all alu parts.
 
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