blown forge

[jacob7]

Trying to get all the equipment ready for a blown forge using an old air tank that measures 12' dia. x 20" long. this will give me about 904 cu inches inside the insulating blankets. I am trying my hand at welding damascus, it's interesting stuff especially the feather. Is this a good size or should I cut the size down? also i really want to use only one burner if can but probably need more than one with this size but do I need this size? If you all were doing this project with all the hind site what would be the optimal size and how many burners. I'm trying to get as much as possible right the first time. Everything else will be from Ray Rodgers tutorial or close. It won't be use for anything else because I have a Evenheat Kiln for heat treating.

[Ray Rogers]

A smaller container would be more efficient. How do you plan to make your damascus - do you have a hydraulic press or power hammer? If you do, then you can make larger billets. If you will be working by hand then you'll make very small billets and for that an smaller forge interior would be better. A section of 8" stove pipe would be good. Or, go to your local hardware store and buy some sheet metal and roll it into a tube shape of 8" and secure it with stainless screws, then build from there. With a single burner and 12" length an interior of about 300ci should work pretty well....

[Doug Lester]

Make sure that your blower puts out plenty of air. My first blower was rated at 60 cfm and I had to run it wide open and had little flexibility. If I tried to cut back the air there was not enough pressure to keep the gas from burning inside the burner tube. What I have now is a blower from a bounce house that I got used off Ebay for $60 plus whatever the shipping was. It gives me plenty of pressure at what ever I have the flow set at with the gate valve. It has also given me a lot more flexibility in my forges.

I agree with Ray, you just don't need that kind of volume. Even if you can get it up to welding temperature, your forge will be an absolute gas hog at that temperature regardless of the number of burners you have on it. I would cut at least 6" off the length and line it with four layers of 1" ceramic matting if you want to stick with the tank that you have. Maybe even cut it in half unless you are thinking about making a lot of swords. Put a pass through port on the back that you can block off.

To be honest, the forge that I use the most is only 7" deep and it's a lot handier to treat short blades in it than in my longer one, 16" deep X 4", more or less. It's fussier to get the fire balanced in it but I'm pretty sure I can get it up to welding temperature (I haven't figured out how to rig a thermocouple to it yet). It's cast from a refractory.

Doug

[jacob7]

I am going to have a hydraulic press so I can make bigger billets which is my plan

[jacob7]

Does the feather damascus during the cutting process have to be in the vertical position? That was my concern. I also don't like pay the gas company very much.

[jacob7]

I also have a portable propane tank which are 12'x10" long. Calculating the insulation inside would be 8'x8 with 402 cu. inches. Does that sound better and can I get everything done?

[jacob7]

I make fixed blades and no swords.
Thanks

[Doug Lester]

You do not need an inside diameter of 8". Whatever it will do 4" will do more economically and I definitely would not go over an inside diameter of 6" unless I was build a forge to handle something like bearded axes and I would reserve a forge like that for just such a purpose. You will just be burning up a lot of fuel that you don't need to. Four inches should handle the widest knife that you should ever want to build.

Doug

[Ray Rogers]

I would still rather see you start with a smaller forge body instead of trying to stuff enough wool into a big body to make the interior smaller. If you do that, it will take longer to reach welding temps because you have to heat all that insulation and IT'S INSULATION which means it does not transfer heat through it easily. There is even a school of thought that says that this added insulation actually reduces the overall insulating efficiency of the total. Whether you accept that or not, more insulation costs more and it does soak up a lot of heat.

Doug may only be thinking of blades when he says 4" interior. That would work for very small billets but since you specifically said you want to do feather pattern I'm thinking you may need a 6" interior since feather pattern is usually done with a pretty tall stack. Anyway, figure out your billet size and give yourself an extra inch or so in interior height....

[Doug Lester]

Not having made a feather pattern damascus, or any damascus successfully, if you need a six inch diameter to weld it up then make a special use forge to do the welding in but use a smaller diameter forge for general forging or you will be burning up a lot of gas. Not an unusual situation for smiths to find themselves in. Anyone can use two or three forges. Instead of coating your lining with something like a mortar you could coat it with a refractory like Mizzoue which is pretty much impervious to flux, unlike products like Satanite, and will hold heat better. But Ray is right, the less you have to heat up, all else being equal, the faster it will heat up.

[jacob7]

thanks for the suggestions. I appreciate it.