[Andrew Garrett]

I'm pretty sure I just made a knife from cast iron.
I aquired an old Fairbanks Morse & Co double open-end wrench--most likely a 1920s vintage.
I hammered it out, ground it, heat treated it, finish ground it, and etched it. It felt like I was working tool steel the whole time, but the etched finish looks different than I expected.
It hardened fine--easily passing the file test.
I know they made cast iron wrenches a century ago, so I'm fairly convinced that's what I have here.

I just made a brittle knife, didn't I?