Bicycle Mechanics - Ideas on how to remove a stripped square taper cartridge bottom bracket?

I have a Canonndale frame that has a cartridge style square taper bottom bracket that I would like to remove. However, the splines that are to engage the removal tool are stripped on both the drive and non-drive sides! Is there any way to remove this ruined bottom bracket at this point?

Thanks

Chisel a notch in it and bang it around with a hammer and old screwdriver?

If you have access to a automotive bearing press, you can use a Dremel, file or even a chisel to remove most of the inner rim of the more damaged lockring, then supporting the frame by the BB shell, press the entire cartridge out. Then you have easy access to remove what's left of the rings. This can be easy or difficult depending on how corroded they are, and you'll adjust the technique accordingly.

If you don't have access to a press, it's basically the same, but you'll use a short length of pipe braced on an anvil or heavy vise to support the edge of the BB shell, and drive the BB spindle by brute force hammering.

With either technique, the amount of force depends on how thoroughly you remove the bearing support rim from the lockring. Stock up on beer, it may take a while.

With either technique, the amount of force depends on how thoroughly you remove the bearing support rim from the lockring. Stock up on beer, it may take a while.

Hmm, hammers + beer + thin-walled tubes. Sounds like a new frame might be in his future! :)

Which cartridge square taper BB?, I cannot imagine how a Shimano one will strip the splines

unless a strong stubborn person kept turning it the wrong way , steel left side ,
and tightened it excessively, expecting it to loosen.

Unless the splines are totally gone, I would look up the Sheldon Brown hint for removing pesky bbs.

Unless the splines are totally gone, I would look up the Sheldon Brown hint for removing pesky bbs.

Does this involve bolting the BB tool to the crank spindle?

Sometimes you have to do that when the splines are intact. Like when the factory neglects to grease the BB threads before installation. It's a good idea to bolt the tool down regardless, even if the BB isn't seized, to prevent slippage and injury.

Go down to the hardware store and pick up the proper fine thread M8 bolt and some washers to bolt the tool down. If you have a vise available crank the tool down in the vise and spin the frame. Otherwise, set the frame on the floor and push the wrench using the frame for leverage. Make sure you're trying to spin the BB off in the proper direction. Sheldon will show you the way.

Is one side plastic? If so take the drive side out first then attack the plastic side, cut it, notch it, crack it, whatever. Should be easy enough. Be careful not to damage the BB shell threads. If it's metal it's going to be a bit more tricky.