With my tax return on its way, I'm going to upgrade my forge.
I want to be able to heat treat blade lengths of up to 12".
On to the questions...
1) Do I need to have a burner with a blower? Or will an atmospheric burner do the job? I don't really intend to do too much forging, just heat treating.
If you just want to do heat treating, I'd say that not only a blower isn't necessary, but I'd steer well clear of it!
What you need is EVEN heat. Much better to add a second or even third burner than resorting to steroids for the existing one.
The only thing you'll probably obtain by putting an unique, hard blowing, superhot burner is a hot spot.
And you don't want that in a heat treating forge.
I don't think a blower is needed at all in a properly built forge, unless you work at high altitudes.
I've done welding in an atmospheric (Venturi) gas forge. A well built atmospheric forge is already hot enough to burn your steel into kingdom come.
Thin atmosphere at, say, 3000 or 5000 ft height may leave you with too little oomph in your forge to reach welding temp, and a blower may help you there, but the burner has to be properly done anyway.
2) If I go to a junk yard, what kind of pipe do I ask for, for the forge body? (I was thinking of something like an 8" pipe? What dimensions do I need?)
That depends on the size of stock you intend to heat.
I'd go for something larger. Why?
Because since you are upgrading your forge, let's upgrade it seriously. Allow enough room for stuff you may want to heat in the future, and for some refractory plate to avoid corrosion of your ceramic fiber if one day you'll want to heat a billet for damascus, with molten borax falling down ready to wreak havoc on any soft refractory around.
I'd go on something 10" in diameter.
I have an old air compressor can for my gas forge project.
3) I'm going to buy a burner somewhere (I definitely don't trust myself to not make a bad burner...
) Will a 3/4" venturi burner like the one at Ellis Custom Knife Works work?
I've worked with something like that. As long as it's properly built, a venturi will do everything you need and still have enough heat to munch away your steel if you forget it in the forge. TIP: The nozzle is EVERYTHING..
I don't know how it's done, but I know this: bad nozzle, and no amount of gas pressure, air or whatever will make the burner burn hot.
Proper nozzle, and there you go, with a venturi and just a breath of gas from the can!
4) I've seen the burners attached to the forge body in different places, between an inch or 2 off from the top, and coming in sideways. Does it matter? If so, what is the best angle?
I used to believe that a cylindrical shape and a tangent burner were essential for proper, uniform heating. Now I think that this attitude derives from trying to put overly hot and powerful mini-burners (i.e.: burners with blower) in an insufficiently insulated forge.
You see, what you want to obtain is a sufficient flow of heat, not a high temperature. You may obtain heat through temperature, sure. But that's not the proper way.
Much better to have a large amount of hot gases, at the CORRECT temperature flow in the forge, rather than a small amount of gas at a MUCH HIGHER temp.
I've worked with a properly made gas forge, which was MASSIVE in insulation, with BIG burners firing straight into the RECTANGULAR cavity, and the steel heated up evenly. Why? Because there were three big venturi burners gently blowing into the thickly insulated chamber. After the forge was properly heated, the walls alone radiated probably more heat than what the burners put in. The heat was built up inside and STAYED inside: the burners just kept everything at the proper temp compensating for the heat escaping from the forge mouth.
This said, since I have a circular cavity in my would-be forge, and angling the burners to get a swirl of hot gases costs nothing, I'd put the burners at a tangent in the chamber. Enough angle to have a good swirl, but not so much that the burner's blow eats directly away at your forge lining.
It's something that has to be adjusted to the single specific situation, there's no "magic angle" or set rule.
Just move the burner in the hole, possibly with a dark room, and you'll see initially a tongue of flame forming a T against the opposite side of the forge, creating a hot spot.
That's too little an angle. If the forge and burner are properly sized, the hot spot will be there just initailly, while the forge heats up, and will disappear once everything is properly heated up. If you still get the hot spot, it means your burners are not pumping enough heat in the forge, while being at a high temperature. If the hot spot in front of each burner disappear, your burners are properly sized.
You may be happy with that, or you may want to take extra precautions angling them. Since you already have a circular cavity, and angling them costs nothing, do it.
Angle the burner and you'll see the jet of gases become a swirl, and then, moving it further, you'll see one side of the hole becoming really more incandescent of the other side. That's too much.
Angle the burner till you get the swirl, and then some more, but not so much as to have the hole overheating.
Do not prtrude the burner too much in the forge.
edit- Almost forgot.. If I want to add a pyrometer (That's what you call the forge thermometer, correct?), where do I add it (IE: do I drill a hole into the forge body?), and what's a good place to get one.
Thanks for the help
Can't help you there. Don't have the faintest idea.
