Lye to the rescue (not soaping)
My husband managed to get aluminum melded into his drill press bit. Nothing would budge it out - I guess it was semi molten, jammed up in the ridges instead of flying out and hardened into it (it actually looked like the bit ridges were completely torn up). He was contemplating having to order a new bit and put his project on hold when he remembered he has a soaper at home.
50% lye concentration to the rescue!
It ate every teeny piece of aluminum off... now his bit is just like new.
It did foam up, put off nasty fumes, and heat quite a lot so I'm glad we did this experiment outside in a double container (which will be chunked).
A learning experience is one of those things that says, 'You know that thing you just did? Don't do that.”
― Douglas Adams