Corin

The Perfect (Most Versatile) Gas Forge

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Ha so this is a can of worms and I bet you all had some ideas of your own when you saw this topic!

So...

Here is the question, what is your idea of the perfect gas forge? I want to generate a reference list of characteristics that every forge builder should consider when settling on a design. Sure such a list probably exists someplace on the net, but I am keen to hear your own thoughts on what makes a forge better than just good.

I have worked on probably over 50 different forges over the years. Servicing burners, tuning burners, modifying burners or just making other peoples projects work. Working on forges got me into blacksmithing, but there are so many different combinations of burner and chamber design and some of those combinations are clearly not as good as others, in terms of temperature. There is of course more to the perfect forge than just temps though.

Clearly the perfect forge depends on the job, so lets narrow it down to the most versatile forge

The key things I have been asked to do to forges will give us a start.

1) The ability to reach welding temps and beyond, in a reasonable time.
2) The ability to control primary air and hence minimize oxidization of material
3) must heat up reasonably quickly, say less than 5 minutes
4) provision for a thermocouple or pyrometer to sense temperatures for heat treating.
5) must be reasonably efficient on fuel.
6) Have idle and full flame control, so it can be easily turned down but not off.
7) Must be able to accommodate long materials
8) must have a wide enough door for wide and curved materials. How wide is enough?

What would you add to the list? can you quantify any of the above? How fast should a forge heat, how efficient etc.

I look forward to hearing your thoughts on what exactly constitutes the perfect gas forge.

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What I had that met all of those conditions was three forges and a heat treat furnace.



yeah I am probably looking for Utopia! :rolleyes: I definitely think it can be done though, there are a few designs out there that come very close. What were the best features of each of your forges? Why three?

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the perfect forge wouldnt be very fun, because it would kinda eleminate all the fun of looking for, or building another one............I built mine with a lot of those goals in mind and scratched a lot of them off quick, but I think I ended up making a pretty versatile little rig. I think that one thing is true of all most all tools, if it does everything than it doesnt do anything really good, think multitool here.......... they are handy but not a single tool on one is better or anywhere near as good as the tool it actually represents. The question is a good one, and it will make a great thread because lots of guys will share lots of great ideas, cant wait to read them all...... as for my two cents I would have to say that if you want that much control and that much versatility than you should look at electric not gas an induction forge is an amazing piece of equipment that pretty much does everything on your list

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the perfect forge wouldnt be very fun, because it would kinda eleminate all the fun of looking for, or building another one............I built mine with a lot of those goals in mind and scratched a lot of them off quick, but I think I ended up making a pretty versatile little rig. I think that one thing is true of all most all tools, if it does everything than it doesnt do anything really good, think multitool here.......... they are handy but not a single tool on one is better or anywhere near as good as the tool it actually represents. The question is a good one, and it will make a great thread because lots of guys will share lots of great ideas, cant wait to read them all...... as for my two cents I would have to say that if you want that much control and that much versatility than you should look at electric not gas an induction forge is an amazing piece of equipment that pretty much does everything on your list


Thanks for the input mate! I You right about the fun thing and probably about the electric forge too I have no experience with them... but I will be sticking with gas! I think a lot of people who build forges tick a few things off the list, some more than others... I am happy with my own but like your multitool analogy it does have limitations. I would still love to know what the generally accepted heating times from cold to forging and welding temps are, and the ideas on minimum width of door too.



Define perfect!


I tried to in the original post, but clearly this was always the weakness in the discussion :rolleyes:

"Clearly the perfect forge depends on the job, so lets narrow it down to the most versatile forge" for the widest range of uses.

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Mine is pretty quick not sure how long, but if I lite it and then kinda get my tools organised and ready to go then double check the area and make sure all is well and im ready to start its usually right there, unless Im doing something really thick........ as for door sizes, I made a door inside a door for my front , which I kinda like thus far I would post a pic but Im struggling with fihuring out how to do that in a reply at the moment

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file size is to large is the issue with pic, but if your on facebook you can get to my facebook threw here and I have pics of it on there if you wanna take a look at it

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Ok so perfect is not the best for all.. So here are a few thoughts. I use a commercial gasser and a homade. Neither of them have or need mixture adjustments. I have forged in below freezing weather and in hot sunshine. And from 1200 ft elevation to near 7000ft. A fast heating forge if yoiu think about it also loosses heat faster. Great for somethings. but my homade has thick insulation that takes a while to heat up. After that I shut the burner off when forging either by hand of power hammer, then turn gas valve on and it lights itself from residual heat. Same with doors. A farrier that heats shoes and an occasional tool for a tune up has a predictable door size need. Other smiths may require so much variation in size of forge and door they do as Grant did and use several forges.

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Mine is pretty quick not sure how long, but if I lite it and then kinda get my tools organised and ready to go then double check the area and make sure all is well and im ready to start its usually right there, unless Im doing something really thick........ as for door sizes, I made a door inside a door for my front , which I kinda like thus far I would post a pic but Im struggling with fihuring out how to do that in a reply at the moment


I just checked out your door design... sorry but I am going to have to steal that for my next one! That is a great solution and would be a significant improvement on mine I use door reducers cut out of ceramic wool and cemented, they work OK but inevitably crumble away and break.


Ok so perfect is not the best for all.. So here are a few thoughts. I use a commercial gasser and a homade. Neither of them have or need mixture adjustments. I have forged in below freezing weather and in hot sunshine. And from 1200 ft elevation to near 7000ft. A fast heating forge if yoiu think about it also loosses heat faster. Great for somethings. but my homade has thick insulation that takes a while to heat up. After that I shut the burner off when forging either by hand of power hammer, then turn gas valve on and it lights itself from residual heat. Same with doors. A farrier that heats shoes and an occasional tool for a tune up has a predictable door size need. Other smiths may require so much variation in size of forge and door they do as Grant did and use several forges.



I probably should rename this thread the most versatile gas forge... perfect is the wrong word, sorry about that.... anyhow, there are some interesting comments there.

I would not own a forge without air adjustment, for two reasons... 1) I work in the combustion industry and it is a point of pride to ensure the combustion in my forge is adjusted correctly to the application, and 2) I use my forge for heat treating near finished products (knife blades and machined die sets normally), and when heat treating I do not want any scale to form. I do not know how to prevent the formation of scale without air adjustment (in a gas forge). I can machine a die to within a few thou and hold it at 900c (1650 f) for 10 minutes, quench it in oil then pretty much wipe it clean with only discoloration and very very little scale if any. Without air adjustment I would have to rough machine the die, heat treat and then after hardening and tempering, re machine hardened steel,
Knives are exactly the same. The less grinding or machining I have to do on hardened material the happier I am. On the other hand the over rich mix I use for HT is terribly inefficient so when heating up from cold I open up the air and give plenty of gas.... If I do that it gets hot enough to melt 1/2" round steel bar in about 2 1/2 minutes.

I don't understand why a faster heating forge would loose heat faster.... would that not depend on the amount of heat you put in and the type/ thickness and quality of refractory?

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Actually a poorly insulated forge will lose heat faster. I think what he is actually making reference to is "thermal mass". Fiber insulated forges can change temperature quickly, hard brick forges take longer to heat, but cool down more slowly.

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I have no idea if this would work in your application, but we always wrapped tool steels like a2 or d2 in a stainlesss foil before heat treating, basically creating an air tite container for each piece may help with need to control air so much, or it may not I am no expert. The thermal mass cool down effect is readily visible in mine, I have ceramic fiber all the way around, with a brick work shelf the bricks dont get to temp quite so quick, but they glow a long time after she is shut off, the IC10 coating really helped with evening the heat out too. The biggest complaint I have is width. My next one will be wider for sure, I am very limited on scroll work due to the size and shape. So I definately would like something bigger eventually, so Im thinking wide and not so tall chamber would be better than my basically round one.

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Actually a poorly insulated forge will lose heat faster. I think what he is actually making reference to is "thermal mass". Fiber insulated forges can change temperature quickly, hard brick forges take longer to heat, but cool down more slowly.


Good point!


I have no idea if this would work in your application, but we always wrapped tool steels like a2 or d2 in a stainlesss foil before heat treating, basically creating an air tite container for each piece may help with need to control air so much, or it may not I am no expert. The thermal mass cool down effect is readily visible in mine, I have ceramic fiber all the way around, with a brick work shelf the bricks dont get to temp quite so quick, but they glow a long time after she is shut off, the IC10 coating really helped with evening the heat out too. The biggest complaint I have is width. My next one will be wider for sure, I am very limited on scroll work due to the size and shape. So I definately would like something bigger eventually, so Im thinking wide and not so tall chamber would be better than my basically round one.


The foil thing does work and is used just as you describe I have seen it on a knife forum, It works incredibly well, better than air adjustments. Having said that I still believe the most versatile forge is one in which you can adjust the air for operations such as this. The result is not bad, even pretty good, though it does require constant monitoring of temperature and continual adjustment to ensure a good result. I heat treat once a month, its no big deal, and not worth the foil...

I too find the door on mine very limiting and yours I note is even bigger! In the last couple of years I have wroked on more and more 20Lb cylinder forges with doors in the side. Normally as high as the ones with front doors. These were all owned by farriers doing the big horses, Clydesdale and such. Great concept but poorly executed because they all had the same problem, very hard to get stuff hot with a gaping hole in the side of the forge, still with your front door concept applied to the side, or front and side doors it my work really well, and would definitely add a huge level of versatility. The side door should be no higher than 2-2.5" though if the ones I have seen are anything to judge by, and you would need to play with the position of the burner so that the flame does not just shoot out the side.

A tall chamber is very beneficial in terms of combustion, the hottest part of the flame, is the tip of the light blue turquoise section where the dark blue starts. If you do not have enough height you will get a cold (relatively) spot under the burner and circular forges carry the heat in a swirling motion, also normally better than square forges.

Here is a typical forge burner flame. you should be aiming to have the floor of your forge about a good couple of inches" longer than the length of the light blue section from the burner nozzle.

highflame.jpg

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