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First attempt at building gas forge-Using plumbers torch parts for burner??

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Life's circumstances and challenges (both large and small), have prevented me from doing any blacksmithing for a very long time. One of the main reasons for that is the only coal available is either very expensive, or too far away.

Recently I started entertaining the possibilities of building a propane forge, and have been thinking that one of those mini forges made from a coffee can or a couple fire bricks would be a simple and relatively inexpensive place to start. My short-term goal is to (at the very least) build something sufficient for heat treating the several small blades I have already forged. 

I've done some research and noticed that a lot of people use those bernzomatic swirl torch heads, but those I have seen are far too expensive for something that seems pretty limited.  I was curious to know if it is possible to utilize my existing plumbers torch by modifying the existing nozzle, or putting together a new nozzle and tapping it to screw on. I would much prefer to piece something together from stuff I already have, that would potentially work much better. Cost is a factor, and for now want to avoid buying anything else if I can help it.

I know that I will eventually need to buy a regulator, but.....Doesn't the knob on the plumbers torch already do essentially the same thing, and be sufficient for short term use?

I already purchased a 20lb tank of propane with a hose fitted to match the small 1lb propane bottles. I and also picked up a couple feet of kao-wool type liner and 2 soft fire bricks from the local pottery supply shop, so I should have enough to get something put together pretty soon.

Thanks for any advice you guys may have. 



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You're golden now just keep the tip of the torch out far enough it doesn't get too hot. By "out" I mean back from the fire contact area in the forge chamber, just poking it into the Kaowool a little bit is plenty to prevent it from entraining fresh air and will keep it from over heating.

Frosty the Lucky


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Hello everyone!

I tried the regular plumber's torch and found the results to be much less than what I think I'll need to get blades up to temperature.

I was cruising the net and found what information I needed. https://www.youtube.com/watch?v=5uuTqCsoOLE

This tutorial was especially appealing since I have a box of random copper tubes, discarded torch parts and brass pipe fittings that I have accumulated over the years, and would not need to run out to purchase a lot of stuff to make something usable.


Since a lot of these parts were the type needed for the burner build, but the wrong size, it made more sense to get an inexpensive tap and die set ,than to go out and spend more for the correct sizes of pipe fittings.


The tap and die set didn't have 1/8" NPT in it, so I had to make another stop at a favorite little used tool shop down the street from my house to get them. Along with those I also found an old Halide torch, extra pipe fittings as well as a burner tip with a small diameter hole, all for around $4



I quickly threw this together after doing some cutting, drilling some holes and re-threading some fittings.




This hodge-podge of parts doesn't light without covering the air ports with tape. After poking holes in the tape, it does produce a weak, jet-like flame.

I was hoping that those of you familiar with the mechanics of forge burners might clue me in to what might be going on here







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It's pretty unworkable from my experience. Maybe if you tinker with it long enough you might get an acceptable flame from from it.

With the recent price increase in plumbing and brass fitting it costs me upwards of $10.00 to build a 3/4 T burner and about 20 minutes if I don't chuck it up in my lathe, if I do knock 5 mins off the time. A drill press and half an hour is really all you need to make and tune a 3/4" propane burner.

Of course if tinkering around is what turns you on instead of forging. . . .

Frosty The Lucky.

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#1 After researching different burner types, the main thing preventing me from building those is that they all require an f-ing regulator!

That's all fine and dandy if you already have all that at hand, but I don't, and am mostly forced to work with what I have available to me....Which is time, a #20 propane tank and a box of brass pipe/torch fittings.

A little constructive criticism would have been helpful, but I still am able to tinker and experiment on my own.


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Plumbing-type torches can be something of a pain. They are usually quite carefully designed to do a specific job and that job is not heating a forge.

Generally, torches are designed to work in the open air. There is usually some primary air, but the bulk of the combustion air is usually secondary air.

Primary air is air that is mixed with the gas before it reaches the burner. Secondary air mixes with the gas after the burner.

When we put the burner into the forge, it is usually through a hole that is fairly tight to the burner. At best, this dramatically reduces the amount of secondary air available to burn. In most cases it completely eliminates the secondary air supply.

When we look at flame temperature, we see that the temperature achieved varies with the air:fuel ratio. It may not be immediately obvious why this is, so I'll try to explain.

Combustion is a chemical reaction between the fuel (in this case we'll assume it is Propane) and the Oxygen in the air. Like all chemical reactions, there is a fixed ratio at which the fuel and air like to react. If we mix the air and fuel at this ratio, all of the fuel reacts with all of the Oxygen and we will get the highest flame temperature.

We get the highest flame temperature because we have released all of the available heat (the fuel is completely burnt) into the smallest possible amount of gases. If we move away from this ratio, we will see the temperature drop.

If we add more air, we only have the energy released by burning the amount of fuel we have burned, but by adding the extra air we have increased the amount of gases that we are heating. With more"stuff" and the same heat input, the temperature will be lower.

If we add more gas, we get a similar effect: Oxygen availability is the limiting factor in this case. We only have the amount of heat energy released by burning the Oxygen we have, but the extra fuel gas absorbs some of that heat, reducing the temperature.

Once the partially-burnt fuel gas leaves the forge, it mixes with air and starts to burn again, giving the secondary flame usually referred to as the dragons breath. The heat energy released in the dragons breath is outside the forge so does not provide us with useful heat.

The technical challenge you are likely to need to tackle is getting the correct amount of air into the flame to achieve the temperature you need.

Using a Naturally Aspirated (unblown) burner, the way that the air is mixed with the gas usually involves a gas jet, Bernoulli's principle and something that may or may not bear any resemblance to a Venturi. Almost any Naturally Aspirated forge burner seems to be described as a Venturi burner on the internet, even though very few of them actually incorporate a Venturi.

It would almost certainly pay you to research the basic principles on the web.

To be honest, I would not expect many people to have done what you seem to be trying to do. I'm guessing the adapter you bought to let you run a small-canister torch off a large cylinder probably cost at least as much as a regulator.

I spent a happy weekend a few years ago trying to modify a cheap and fairly nasty torch set to work as a forge burner for a coffee-can type forge. The first thing I did was fit the gas jet from the smallest burner into the biggest one to try to increase the air:fuel ratio. It helped, but was not enough. I then opened out the air holes in the back of the burner. still not enough. Then I slotted the side of the burner, which gave me enough.


The temperatures in the photos are in degreesC.

I rather enjoyed playing with it and it performed remarkably well for something so crude. I took it to a hammerin where it did a couple of days of continuous work.

My intention was to try to write it up as a "how-to" that a beginner could follow. However, there were far too many variables for that.

For less than twice the cost of the torch set (and considerably less in terms of time), I can buy an Amal atmospheric injector, a regulator and the parts to build a near-ideal forge burner, easily able to  give stable temperatures everywhere from Heat-Treating to welding. More importantly for me, I can tell someone hundreds of miles away "buy these parts and screw them together", confident that they they will work as intended.

I've not returned to the modified torch setup and the original went in the raffle at the hammerin.


Edited by timgunn1962
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For my one firebrick forge I didn't insert the nozzle, I just put it close to the opening in the side of the brick and aimed it in.  Did a lot of small item forging in my basment during that very cold winter.

As to not using a regulator?  WHY?  I read this as "I'm going to spend 10 times as much money in time and fuel wasted trying to get a sub-optimal system built" 

Shoot I have used acetylene regulators (rated for all fuel use) US$5 at the fleamarket, store bought propane regulators $35, shoot I even bought a turkey fryer set up where the idjit had packed it so the hose flipped out and drug the *tip* of the regulator on the road all the way to the fleamarket.  Wore it to a nubbin.  $2 and I removed the brass tip from a junked BBQ and put it on and I've used that one for over a decade.

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Hello everyone.....Your explanations are most appreciated, thank you for taking the time to type them out for me!

TimGunn Are you anywhere near Baccup/Haslingden by any chance?

What started out as a very small forge heated by a plumber's torch has evolved into something a bit bigger. All I set out to do with this project was to come up with something to work temporarily, while learning and familiarizing myself with the basics of gas forges while hopefully improving my equipment as knowledge and money allows.

I always knew the need to acquire a regulator. The guys at my neighborhood used tool and pawn shops have an interest in my blacksmithing projects and have offered to keep an eye open for me. Also, the beginning of garage sale season upon us, and I seriously doubt it will be long before I acquire one.

My 20# propane tank was purchased off of Craigslist with the adapter hose for $30.... Not a smoking good deal, but not terrible considering that the tank and hose are near new.

Are the burner pics coming through okay?

Thanks again for your comments everyone!








Edited by Brasilikilt
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I'm about 9 miles from Haslingden, maybe 15 from Bacup.

That flame looks like a pretty reasonable starting point to me. There looks to be a decent central cone, suggesting a fair bit of primary air. I've never been able to get a decent photo of a flame because the exposure length blurs out the edges of the flame parts. I'm pretty sure it's just my complete lack of photographic skills, but I find that video tends to show more of what is going on than photos.

For HT temperatures down around the 800 degC/ 1500 degF region, I tend to find I need a very rich flame with a good bit of yellow to it. What do you get when you stick that in the forge, deprived of the secondary air?

I built a 2BF a few years ago and made the burner hole tapered through the thickness of the wall: narrower at the chamber end. This gave me some secondary air adjustment by moving the torch in and out. It seemed like the obvious thing to do and I didn't really think much about it at the time. It did let me get pretty good temperature control over a few minutes of soak time. It might be worth a try.


Edited by timgunn1962
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 megr-6120-large.thumb.jpg.583eb114a9b270I put the word out, and was able to get one of these 0-60 psi regulators.  It seems to work OK, and is able to cut the gas off completely, or flow with enough pressure to blow the flame out. I'm guessing that's what it's supposed to do....Right?

After hooking it up to my burner, the flame isn't as good as it was when connected through the torch valve.... Any idea why that might be?

Also, I need to complete the body of the forge itself by coating the insulating wool with the appropriate clay or cement. Testing the forge out right now blows a lot of particles in the air (which according to the mfr. are broken down harmlessly by bodily fluids) I still  don't want to risk inhaling it!

After calling a fair amount of suppliers in my area and only finding 55lb sacks of refractory for sale, I ordered a tub of this stuff http://www.lowes.com/ProductDisplay?langId=-1&storeId=10151&catalogId=10051&productId=3572462&cId=detail   It's rated up to 3,000 deg. and should be enough to do the trick...for a while at least. For $13.00 with free shipping it was an attractive option, as I'm sure it will do a lot better than plaster of Paris cut with sand!

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