Removing a crank with a destroyed thread

[Punkawallah]

Still working backwards: does anyone have an alternative to a blowtorch to remove a cheap and nasty plastic cup-and-cone bottom bracket?attempts to remove it conventionally just broke the plastic (and yes, I was turning it the right way).

I’d avoid a blow-torch. The burning plastic could give off all sorts of noxiousness (even for a bike workshop), and if it melts into the BB threads you’ve got another headache. This might give you ideas, although the BB concerned was aluminium in steel:

View: https://www.youtube.com/watch?v=SPHD9VMj43U

 

[Punkawallah]

But make sure in Space first

It’s the only way to be sure ;-)

 

[Ajax Bay]

Echo caution with caustic soda. A father of our son's fellow U10 rugby team member used this on a sink and is now blind in both eyes.
On the BB's plastic cup (left hand side), which is now broken beyond repair, I had this problem - the 20-spline tool munched the plastic - but I got it out by unscrewing the drive side cup. However this option is not available to the OP till he cuts off the crankset.

 

[rogerzilla]

Hacksaw and chisel is what I've used.