The problem with recycling is you never REALLY know what you are using. But if you want to make a servicable knife, you might be pretty well off hanging onto that sawblade. You could do some testing to check to see if the steel is suitable for knives. (Note I said serviceable, not a superior knife.)
Many old big sawblades are L-6 or its relative - 15N20. I understand that some of the newer ones could have bimetal blades - ie.- the blade tips are a high speed steel like M2 and the body and centre are a plain carbon steel like 1050 or 1060.
You need to cut a piece and quench test it to see if it suits your purposes. Personally, I'd cut away the portion on the cutting tips and use the material towards the inner 1/2 just to be safe. Jason.
