Question about mixing old scrap steel with new stock

I grabbed a bunch of old leaf springs from a scrapyard in Akron last month to save money on knife making. Three blades later and two of them have hairline cracks after heat treat. Is there a reliable way to test mystery steel before you spend hours forging it?

3 comments

3 Comments

alice8921d agoMost Upvoted

Pile on with my own story here: I've totally been there with mystery steel and it's the WORST when you put all that work in and get cracks. I picked up some old truck leaf springs once and tried three different heat treat cycles before I got one that didn't crack, and that one still warped on me. Susanm56 has a point about just buying known steel, but if you're like me and hate spending money when free stuff is around, the magnet and file trick rileyb61 mentioned is a lifesaver. I also do a quick spark test on my grinder - if the sparks fork and burst like a firework, it's probably high carbon, but if they just dribble off dull, it's trash. For leaf springs specifically, I always normalize them twice before heat treat now, because that seems to help even out whatever weird alloy they used.

rileyb6121d ago

Man that's rough, I've been there with mystery steel and it's a real pain when cracks show up after all that forging time. I keep a little magnet and a set of files in my shop just for this sort of thing. If a file skates off the surface without biting in, that's usually a sign of high carbon or tool steel which is good for blades. But leaf springs can be anything from 5160 to 9260 or even some newer alloy blends that act weird during heat treat. Before you spend hours on the next one, try grinding a test coupon thin and hardening it in oil see if it snaps or warps before you commit to a whole blade.

susanm5621d ago

Why bother with all that testing when you could just use known steel from a supplier and skip the guesswork entirely? Leaf springs are often recycled for a reason, and not every mystery piece is worth the hassle of figuring out its quirks. If you're spending more time testing than forging, maybe the real problem is starting with junk material in the first place.