Andrew, thanks -- I'm not sure what laurel, there, is... Here we have all kinds of things called laurel, depending on where you live in the country, or what you've planted as an ornamental. Have you got a genus name for the kind you have?
Re. cyanide containing pure compounds here. The discussion is making me uncomfortable, since my hope was finding safe and readily available ingredients and methods for case hardening as alternatives to those compounds. I think it may be possible to do that, and I hope, with reductions in the need for prolonged high temperatures in a traditional pack case hardening method. It would be nice to have a method which provides a thin case for hardening taps and cutters for occasional use that took a half hour or less, and didn't consume large amounts of fuel in the process. Or require a specialty oven.
That's my hope. I can't stop people from pursuing cyanide chemistry for case hardening, but I hope great care is taken, and the risks are not minimized here in this thread (ie. is cyanide gas more or less dangerous than hydrogen sulfide). And people realize that at elevated temperatures and in combination with other compounds, a little bit of knowledge here is NOT sufficient. Further, as has been mentioned, there may be restrictions on commercial availability now for legitimate reasons.
That is why I started his thread - to find a useful alternative to all of these potential issues. The experimentation I hoped for, and hope to do, is in trying alternatives.