recommended size for welding forge

[jdale]

I just finished my 20 ton shop press and all that is stopping me from making some Damascus is a forge that will reach forging temps. I am planning on using a forced air burner and have a 11 gal propane tank for the body.

A quick calc shows an interior volume of the tank at just under 1450 sq in. Is this a good size for a welding forge? If so how Much kaowool/ Samnite should I put in for insulation? Any help would be appreciated.

[WynnKnives]

I have yet to get into forging but always have wanted to... but I will be lurking on this thread for sure.

[Ray Rogers]

You don't want your forge to have much more volume than you need, generally that would be 300 to 600 cubic inches for a 6" to 8" interior diameter that was 12" long. You can, of course, put in as many layers of wool as it takes to reduce the interior to 6 or 8 inches. If that takes more than one layer though then you are creating a forge that is harder to heat, slower to reach welding temps because all that wool has to be heat soaked. That takes either a long time or a really hot burner.

A better solution is to get a piece of 8" stove pipe and line it with 1" of wool. You're in Michigan so I would think the hardware stores in your area probably carry stove pipe. If not, then just buy some metal flashing (a roll of thin sheet steel, not aluminum). Roll it into a tube and secure it with screws and your forge body is ready for insulation. This doesn't need to be a big production and the thinner, lighter forge will heat up quickly.

Now, about that blower. You mentioned in another thread a few days back what you had but I forget exactly what it was. I do remember that I thought it sounded puny. There are thousands of tiny squirrel cage blowers out there, some with really high ratings like 400 cfm but they are useless as a forge blower. The reason is that they only work when there is no resistance to the air they are putting out. Try to put that output through a 1" burner tube and you might scarcely be able to feel it blowing through there. A good forge blower will be rated a minimum of 100 cfm but it will also be capable of providing 32 to 40 ounces of static air pressure. Very few blowers actually show that rating so the best clue you can get is to look at the horsepower and amperage or wattage rating on the motor. The motor will probably be in the 1/2 hp range and draw 150 watts or thereabouts. You can try the blower you have but if it seems to perform poorly now you know why that might be.

It made me smile when you said all that was stopping you from making damascus now was building your forge. That might be true, but let's wait until you have a forge and then see what happens. If it doesn't work out right away we will help you iron out the bugs ...

[jdale]

I saw a posting on here a while ago, I believe it was a moderator or one of the 2000+ posting members. He used a bathroom fan in his welding forge, He said it was 70 cfm rated. I figured I would try it out, if it doesn't work I'll just switch out the blower as it will keep the same pipeing.

For the body I will scrap the propane tank I started working on earlier. I have a double insulated stainless steel section of 8" stove pipe I'm not going going to be using in my wood stove. Should I remove the insulation that's in it or just attach the burner inlet?

I am hoping that the forge is the only thing I need go try Damascus. I ordered a bunch of 1070,1084, and 15N20 from Aldo got my 20 ton press squishing everything I can get my hands on, 20 mule team borax, 2400 degree rated thermocouple, and every website and posting I can read as well as end caffery's DVD on basic Damascus

[Ray Rogers]

You can leave the insulation in the pipe if you want to, the most it can do is melt and that shouldn't hurt anything. A single walled pipe would have been enough.

20 Mule Team Borax gets used but it isn't the best. What you really need is anhydrous borax - no water in it. Kelly Cupples sells it.

The steel you have should be fine and you seem to have access to a lot of good information. What I was grinning about is that the real world often differs from theory. All the cleaning and prep work is hard, dirty, and slow if you get it right and it doesn't stop until the billet is finished. The speed of your press may be an issue. If it is, it can probably be dealt with by making either a larger or a smaller billet than you had planned on. And, the initial weld can be very tricky, it doesn't work the way most people assume it does although since you have those dvds you probably already know that.

Whatever happens, it won't be boring ...

[jdale]

With construction season starting i have had little time to work in the shop, but i did get some time today. I decided to go with the propane forge as i was incorrect about the inside dimensions, and it seemed easier to work with as it has a closed top and bottom. Without any insulation the dimentions are 9" by 12" so by the time i get 1" of kaowool, sanite and itc100 i should have a volume of just under 350 cubic inches.

The front opening is 3" by 3.75", the rear opening is 2.75" by 1.5".

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[Ray Rogers]

I'm not quite sure where you want to go with this design. Looks like you're building a vertical forge. That's fine, except that the bottom is usually open (or partly open) on such forges to allow flux and crap to fall through. You can open your forge for cleaning and that's good but after flux cools it can be pretty hard to remove it.

On the other hand, you probably just haven't got that far since you haven't started to mount your burner yet....

[jdale]

I have heard from a lot of people that the hole in the bottom of the forge gets quickly clogged up. I was planning on making a bowl out of Samnite filled with kitty litter to rest on the bottom. That way when it gets full I pop it out and drop in a new one. That and I am going to Mount the forge, blower and tank on a 2 level steel cart, a hole in the bottom would cause quite a mess.

[Ray Rogers]

That sounds like a plan. No one around here is likely to say there is only one way to do any given task. It's hard to come up with anything completely new but there are infinite variations on just about everything ...

[Naboyle]

I recently acquired a piece of 12" stainless pipe, 16" long. I decided to make another forge but this time a vertical one. I read a post on another forum with a posting from Ed Caffery where he split his pipe and added a 6"piece to make an oval forge. So I have started to do the same thing for my new one. I got all stainless fittings for the burner. Wouldn't want the forge and burner not to match anyway Ray I see you saying about the bottom not being open. So should I leave the bottom open? Or do I put a plate on the bottom? I've seen people talking about cat litter on the bottom. Is there no bottom on these forges? kinda lost here. I don't really understand. I have insulation and I just acquired 2- 55lb bags of refractory. Sorry to hi-jack the thread but the open bottom has me confused. Don't wanna be welding in plate if its not necessary.

[jdale]

Don't worry about hijacking, the more information given will always help.

I picked up all the fittings for the burner today. I found a design on I forge iron.com which looks promising. The only problem is I can't find any black pipe larger than 1". I plan to have 15" or so of 1" black pipe from the inner forge chamber to the 1" to 1.5" reducer but after that I can only find galvanized pipe. I don't think there will be an issue with heat that far back, or will there be an issue?

[Naboyle]

I dunno but I won't use it for anything. And when I run into it at work I'll always wear a respirator anytime I have to cut or weld it. But I do my ####edest to steer clear of it. I have an great supply and assortment of pipe and fittings from our storeroom at work so I don't even have to go to the stores to buy that kinda stuff. That's why I went with all stainless. It's readily available for me.

[Ray Rogers]

I think the bowl in the bottom sounds good but I've never tried it. To use kitty litter you need a bottom, with an open bottom you don't need kitty litter but some of your heat goes out that way although that probably doesn't matter much. It's worth a try either way ...

[metal99]

What are the pros/cons of a vertical forge compared to a horizontal forge?

[jdale]

Im having design issues, im trying to get the entire assembly to fit on the cart. But i am unsure how much black pipe i need before i can safely use galvanized. I have seen lots of pictures where only a few inches of black pipe protrude from the body of the forge, but im gun shy about potential fumes.

I am also wondering if i should mount the forge opening at the front or side of the cart.

Here is the ammount of space i am working with
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