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Went out and picked up a cheap 30lbs propane tank today for a new forge build. I went with 30lbs just to get a little extra length, and buying it brand new with no propane eases my mind as I get pretty paranoid when it comes to propane. 
 

The only thing I’m stuck on is trying to decide between venturi or blown burners. Still have some reading to do there. 
 

Thought about making a little WIP thread over the next couple weeks. I plan on making cuts and sanding the paint off tomorrow. Maybe welding on legs or some kind of stand. I’ll post updates! 
 

This is the 30lbs next to the typical 20lbs exchangeable tanks just for size comparison. 

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Either should serve you well.  Just remember, if you're hammering by hand, you're only going to be able to work 4-6" of steel at a time before you have to reheat anyway.  Honestly, I would utilize the smaller one to build a general forging/welding forge, and save the bigger one for when you want to build yourself a separate heat treat forge.  You'll save yourself a bunch of propane, and the forge will get up to temp much quicker so you'll be able to get more work done as well.

 

I think you'll find a pretty even split of opinions when it comes to blown burner vs. venturi.  If you're thinking about going with a blown burner, check out the pinned thread on them near the top of the Tools and Toolmaking subforum.  They're pretty simple to put together, and very versatile.

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Alex gives good advice.  The usual tendency when starting out is to build way too big a forge and throw multiple badly-designed venturi burners on it in hopes of getting enough heat.  Think about what you want to do.  If it's just knives, a very small forge will do fine.  You can forge most swords in a little two-brick forge, in fact.  That said, it's handy to have a forge long enough to heat treat your largest knives.  I knew a guy who heat-treated full-length swords in an 8" vertical design by stroking the blade back and forth through the hot spot.  Not ideal, but certainly possible.

 

Do you want to make damascus? Then you'll need to be able to weld.  For this you need either GOOD venturi burners (and most are not great) or a blown burner.  Blown burners are easier to adjust for welding, but good venturis are fine too. 

 

Do you want to make axes?  Decorative work? You will need a forge big enough to take the object. and if it's an axe you may need to stick it in the forge halfway folded or at an odd angle.

 

I do most of my work in coal, but I do knives up to around 14" in my two-brick venturi forge.  When I need big damascus, I visit a friend who has a big blown forge and a hydraulic press.  Yet another reason to hook up with your local guild.

 

A quick opinion rant on venturi burner kits: In general, all the do-it-yourself kits and instructions are crap.  The Ward Reducing-T is good, and the Frosty T-burners can be good IF you do your part in aligning everything.  If you see bell reducers on a burner kit, run away.  The one on the intake end is fine, but really difficult to get the right gas jet alignment with.  Bell reducers are not burner flares.  Don't use them on the downstream end.  Avoid anything from Devil's Forge/Hellfire Forge.  They're okay for heat treating, but that's about it. Chili Forge makes a good burner, and the T-rex from hybridburners.com is the Rolls Royce of venturis.  They're also like $250.  The Black Beauty from Anvilfire.com is $50 and is every bit as good, you just have to get creative with adding a choke if you want one. As shipped, they do a good neutral atmosphere.

 

I personally can't abide top-mount burners.  Other people don't seem to mind them.  The key thing to remember with gas forges is that the radiant heat of the lining heats the steel, not the burner flame. It's fine, and often handy, to have a hot spot where the burner flame hits the wall, but I prefer it on the wall rather than the floor.  Top-mount burners also act as chimneys when you turn off the gas.  This can melt the fuel hose if you're not careful.

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Lots of good info. Thanks guys! 
 

My thinking behind the larger forge is that I want to be able to forge weld larger billets, and by using a blown burner, I could save a little bit of propane while also getting the heat I would need. I also just wanted to give myself room for options. I’d rather have a larger forge and not need it than need it and not have it. But maybe that’s just a poorly educated way of thinking. 
 

I definitely want to get into damascus and San Mai and experiment with different tools. Knowing that I’ll need to get to forge welding temps often makes me lean towards a blown burner. I also plan on investing in a press from Coal Iron Works by the end of the year. Super excited to get my hands on something like that! 


So, does my reasoning justify using the larger tank for my forge? Or is that the typical newbie answer that you guys usually get? I don’t want to use the larger one if it’s truly a dumb idea. I guess I figured a little extra length wouldn’t hurt to have! 

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It does depend on your reason, I would think.

 

I got a 40-lb tank just because it's a long drive to the most reasonable filling station and I don't want to do it very often - I only get so many hours in a weekend, and I'd rather spend them forging than driving to get propane.

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Propane forges are like hammers or tongs:  Don't ever think that you can have too many!  One for every need!  

 

That may be a slight exaggeration, but definitely don't ever plan to have one that does everything.  Having 3 is pretty common (general forging/small stuff, forge welding, and heat treating larger pieces like swords).  I can't fit a Dane ax in either of my primary propane forges, so I will either have to make another forge (re-using a burner that switches between two forges) or use the solid fuel forge.  Some day I'll get around to making one, but honestly, I'll probably cheat and cast it.  

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Posted (edited)

Thanks for the information!! I’ll have to decide tonight that way I can spend the day grinding and sanding tomorrow. 
 

I’m kind of leaning toward the 30lb tank because there’s never been gas in it and I don’t really want to purge the other tanks lol. I suppose I can always cut it a little bit shorter and weld the end piece back on. Or make “doors” for the front and back. 

Edited by Seth Carpentier
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I can read... yeah, my FORGE is probably the size of a 30-lb tank (but I made it from sheet metal, not a tank). My tank that I use for the gas is a 40....

 

And I would listen to Alex because honestly mine was so big that I put extra kawool inside to make the interior volume smaller (on the plus side, the outside doesn't get as hot as it once did)

Edited by Ted Stocksdale
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Yeah, I feel like I should listen to the advice I’m given on here. What’s the point of getting advice if you don’t take it into consideration! 
I think I’m going to cut the 30lb tank down to the size of the 20lb since I don’t have to purge that one. I think they’re about the same circumference. 

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Two points.  

 

Mostly, people think about laying the tank down on it's side, which gives you a long burn chamber and a floor.  That tank would make a good vertical forge, like this.  If I need a floor, if I'm heating something small, I throw a sacrificial piece of steel across the bricks.  I have other pics of this, the burner comes in just above floor level, and there is a Kaowool plug in the top.

NF4.jpg

 

Second, venturi burners are nice, they don't need power and, if properly built, they work well.  OTOH, blown burners are simple and they don't need much fussing to make them work.  This thread talks about them.

 

Geoff

Edited by Geoff Keyes
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I did the exact thing they're talking about with mine.

Too big, too much fire in the beginning.

My forge was probably pretty close to that tank in size at first. But I built it out of an old water tank.

 

I wasn't getting anywhere near forge welding temps.

 

The guys on IFI gave me some good advice, frosty in particular.

 

Cut in half lengthwise, reduced my interior volume- and dropped to a single blown burner with a 1" mixture tube instead of 2" all the way in.

 

Difference was night and day.

Before and after.

And my recent attempt at a feather pattern weld.

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Great advice about forges. Here's a (not great) picture of my creature. Welded up some 16 gauge plate into 7 sided shape. Threw a 1.25 inch blown burner on it (go with the 1.25 not the 1 inch if you can. WORLD of difference). 2 inches of kaowool, lined with 0.25 inches of cast-o-lite 30. In the picture below, I had just taken my thermocouple out from checking the temp. Maxed it at 2400F. Interior dimensions are about 4.5 inch diameter and 13 inches long with an exit hole out the back for long stuff. I have done 4.25" high x 4 " long x 1.5" wide  Damascus billets in this and worked it out to 30 inches long. In this case (forge size), bigger is not always better. I love this forge. The ONLY reason I'm debating making a new larger one is I am having trouble working my hearth furnace pucks in this one. I'd hold the 30 lb tank for your propane source. I usually freeze my 20 lb backup every time I try to use it for Damascus welding.

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I got the valve off and flushed the tank with water. It’s sitting upside down airing out right now. I’m going to give it about an hour then flush it out once more. I’m assuming it’ll be safe to take an angle grinder to it after that. 
 

I went and bought a “vacuum purged” 20lb tank from Home Depot so the cleaning steps I’m taking might not even be necessary. Not taking chances though. Propane freaks me out. 

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Leave the water in it when you cut it.  It'll hold still better and eliminate any possibility of kabooms.  Messy, but safe. Once you have one end open the risk is gone and you can cut and weld as you like.

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mines made from a disposable helium tank same size as a Freon tank is ok size for forge welding by hand small when using a press or power hammer next ones going to be a 30 lb propane tank so i can use the press and hammer to full advantage 

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Got the front cut out. Sounds like it’s safe to dump the water now and cut the back. I saw someone on another thread weld three or four small bar stock tabs on the back to bolt the “rear door” on. Might try that so I can take it off when needed. 

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This is it for today. Got everything cut out except the burner hole. Sanded the paint off. Welded two tabs on each side of the back to bolt it on. I’m going to wait until I get it bolted on to cut the bottom of the back hole even with the front. Welded on some angle iron just to keep it upright. I’ll figure out an actual stand for it soon. I feel like it’s an okay start to a new forge! 

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  • 2 weeks later...

I added two layers of 1” 8# ceramic fiber blanket, got it all sorts of rigid, applied Kast-O-Lite 30, wrapped it in a wet towel and sealed it up in a trash bag to cure.. and wouldn’t you know it… I forgot to cut my burner hole :mellow:

 

I’m really hoping I can just drill through the refractory. Thoughts? 
 

Also pictured, my blower came in! Even has a nifty little intake adjustment, although I think I’ll still install something like a gate valve. I’m still searching for a forced air burner plan that I’ll for sure follow. Any links to plans that worked for you would be appreciated! 

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Look in the tools and tool making page.  There is a pinned topic called Blown Burners- a care and feeding.  Geoff details out a super simple design that has worked very well for me.

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