http://www.100megsfree3.com/kragaxe/Furnaces.htmlThese are older forges and furnaces. I still use one of them, but I need to update the description since the operating parameters have changed a bit. I've built about a dozen now and I've got much better at building them. I prefer a Goss 0-40 psi regulator with a gauge, but they run ~$50.
My current knifemaking forge is pretty efficient. I melted part of a leaf spring in it a while back, so it gets plenty hot. Made a nice mix of steel and dolomite.
It uses a 3/4" burner tube, 0.030" MIG tip as a gas jet and generally runs at 4 psi for general forge work, 10 for forge welding.
The big crucible furnace uses a blower and the single burner. It easily melts pure iron. Makes nice glass out of the cat litter in the bottom of the furnace as well. For cast iron and steel I run ~17psi through a .030" jet with a two speed hair dryer as a blower. For aluminum, even at 0 gauge pressure the furnace will quickly overheat the melt if it's been operating long enough to be at steady state. It's at ~2200* then. At 4-5 psi it's around 2400, 15-17 psi...~3000. That's pretty much the max regardless how much more air/fuel I pump in. Good insulation and properly tuning a burner iare the keys.
I'll have a "virtual shop tour" published in the Texas Knifemaker and Collector newsletter in Feb. I'll link it here. My shop is destined to become a superfund site! Hah. Actually, I just want to see the look on some archaeologist's face when the excavate my property and find medieval armour, cannons barrels, knives, swords....and power tools and chemical vats.
