Tried a coal forge after 4 years on propane and it cracked every blade I made that weekend

I finally built a coal forge in my backyard after running a propane forge since I started in 2019. Thought it would be a simple upgrade for better heat control. First three knives all cracked during the quench because the coal fire has hot spots I never accounted for. I had to adjust my steel selection and learn to read the flame color way differently. Took me about 8 hours of trial and error before I got a clean billet through. Anyone else switch fuel sources and deal with a steep learning curve like this?

2 comments

2 Comments

olivia_hernandez12d ago

My first propane forge had a digital gauge and I thought coal guys were just being stubborn about their old school methods. Then my buddy let me try his coal setup for a weekend and I cracked three straight blades before I got the heat right on that fourth one. The uneven temps in a coal fire are no joke, you really have to watch for those dark spots that look cool but are actually colder than the rest of the fire. I still use propane for most things but I get it now, coal takes a different kind of attention.

cameron_webb11d ago

That line about "dark spots that look cool but are actually colder" hit me hard, because I melted the tip off a file on my first coal run thinking a dark patch was safe to dunk in. I spent a whole afternoon treating my coal fire like my propane forge and ended up with a pile of scrap steel before I realized you have to move the work around constantly like you're panning for gold. It's a whole different animal, and I have mad respect for anyone who can nail heat treat in a coal fire blind.