Tried to forge a knife from a railroad spike I found near the tracks in Flagstaff

Spent about 8 hours on it, only to have the blade crack right down the middle during the quench because the steel was too brittle. Lost a whole Saturday and about $40 in propane. Anyone have a good method for testing unknown steel before you commit to a big project?

3 comments

3 Comments

clairen852mo ago

A guy on a knife forum I read swears by spark testing. You take an angle grinder to a small piece of the unknown steel and watch the sparks. The shape, color, and length of the spark stream can give you a rough idea of the carbon content. It's not perfect, but it can save you from wasting time on low-carbon steel like a lot of railroad spikes are. You can find comparison charts online to help read the sparks. It's a cheap way to check before you fire up the forge.

kevin_west2mo agoMost Upvoted

Totally agree with @clairen85, spark testing is a game changer for sorting scrap. I had a bucket of mystery steel from an old factory and the spark test saved me hours. The high carbon stuff threw these long, branching white sparks, while the mild steel just had short, orange ones. It's not a lab test, but it gets you close enough to decide what's worth forging.

alexk602mo ago

Spark testing is cool but I tried it once and my garage looked like a 4th of July show gone wrong. I'm sticking to just buying known steel now.