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Forges 101


Mikey98118

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CANLIB: Glad you decided NOT  try making your own refractory or kiln wash based on some of our musings and experiments. Go with known products until you've been doing this stuff a while. Some of us have been playing with mud mixes in forges for a while, years actually and we're standing back and listening to Maarten's experiments and results rather than doing our own. 

The Betonite type clays are extremely hydrophilic. They can and happily do hold more than their own weight in water and fight a hard fight giving any of it up. 

I wouldn't mix a zirconium silicate and bentonite kiln wash any dryer than latex paint and lay it on like a coat of paint. If the coat is about printer paper thick it can dry without cracks that impact things the next coat won't fill and cover. 

I've about written Veegum off, the % used that turn kaolin clay almost useless are really small. Working percentages seem to be 0.35% and down. To put easy to grasp numbers on it that'd be 3.5 grams to a kilo. and that makes the mix very plastic and  slippery on a potter's wheel. They were saying a couple weeks of dry time before a pot could be handled without deforming and months before bisque firing. 

Unless someone drops a bucket of bentonite and a few lbs. of zircopax on me I'm leaving this to someone else. I've dealt with bentonite and you gotta know it's tricks, if it's soft and squishy it may stay that way a long LONG time unless you live in a desert and even then it'll never be really "dry."

Frosty The Lucky.

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I should have been clearer in the original post. One thing I have learned over the years is to never assume someone knows something, and to never ask how dumb people can be, some seem to take it as a challenge. I should never have "assumed" that someone would think about casting lead without adequate ventilation, although I am sure that there are some people out there who do. And it is better that you made me clarify what I was saying. It may prevent someone from making a serious mistake as far as adequate ventilation.

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Now ,on to the subject of this thread. I have an air tank that is 10" in diameter, and 20" long. I figure that will give me a 5"x15" chamber after 2 1/2" of insulation on the walls and ends of the shell. I plan to use this mainly as a knife makers forge. Maybe a little long compared to a helium tank, but not too bad. I am unsure if I should go with 2 half inch burners or one 3/4" burner. Eventually I want to do a PID controller. All the schematics I can find for plumbing this rig show 2 needle valves, with one set for 100 degrees below the set point, and a second needle valve set for 100 degrees above the set point. When the temperature drops a solenoid is activated allowing the high temp needle valve to receive more gas and bring the temp up. Several people are reporting  plus or minus 4 degrees from the set point. After reading Mikeys book and the entire burners 101 thread and the entire forge thread I still have so many questions. For instance, which burner will tolerate an increase in gas volume with the least negative effect on flame composition? And what is the best way to rig a holder for the thermocouple probe? I know my first gasser will leave a lot to be desired, but an attempt should be made to be as good as possible. I figure the heat control will be a major asset in heat treat. I have been wanting to do some 1095 and eventually D-2, but my 55 charcoal burner is not an ideal heater, and where a magnet is "good enough" for some steels I want to do a little better. Any suggestions will be greatly appreciated.

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If you're going to have a 15 inch long chamber you'll want more than one burner (unless it's a ribbon burner - and even then maybe more than one).  You've probably seen this before, but unless you have a power hammer you'll be hard pressed to work more than 6 inches of material before it cools to the point where it needs to go back into the forge.  So, a long forge means you use more fuel to keep the chamber hot and you keep heating/reheating steel that you can't possibly forge before it cools.  That potentially means you lose more steel to scale and decrease the carbon content of the steel.   In other words, there's no benefit to you or the steel from a chamber that long unless you are doing long twists or something similar which requires long sections to be heated at once.   A shorter forge with a pass-through in the back is usually a better way to go.  The exception is preparation for quenching things like long blades.  However, unless we're talking about swords or very long knives, you can slide the workpiece in and out of the forge to get a uniform temperature before quenching.  Trying to temper in a gas forge with NA burners is probably a non-starter though.

Once a good NA burner is properly tuned, changing the pressure a little bit one way or the other will not have a significant impact on flame composition.  If it's slightly reducing it will tend to stay that way, for instance.  The reason is the components are chosen so that as the fuel pressure increases, the amount of air drawn in also increases proportionately.  In the range you are talking about (+/- 200 degrees - either C or F) there should not be a noticeable difference.

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Yeah, I know about only being able to forge about 6", but the air tank is what I have to work with. And  everything is a trade off,  having more room to heat treat some longer blades is a plus that I have to trade for lower fuel economy.  Not the ideal but a compromise. I have checked with 3 different HVAC companies and haven't found one yet willing to give up an empty Freon tank. I plan on building a burner this payday and will post pictures. I think I am going to end up doing that one with the saddle that Mikey posted about. It appears to me that it has infinte adjustment of orifice from the mixing tube, as well as near complete control of the amount of air. If notches were cut in the reducer it could completely close of the air. I think complete control of those two variables should make it as easy to tune as adjusting an oxy-acetylene torch. Notice I only say "should". The only other variables are orifice size and flame nozzle.

Also, I was thinking that if I can tune the burners to a very short flame I can avoid flame directly hitting the work piece. For aiming the burners I plan on unscrewing the reducer and setting the mixing tube into the burner fixtures on the forge, marking a 1/3 mark on the floor. Then insert a dowel rod into the mixing tube and see where it hits. Adjust the thumb screws for the proper position and tighten them down, and re-install the reducer. Oh, and I plan on buying some flame nozzles from Zoeller Forges supply. And I really appreciate the info about the flame composition, being a rookie with propane burners that was a major concern for me.

I kind of feel like I am getting way side tracked from my original direction and that building different burners could become an addiction ,LOL.

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There's nothing wrong with using the air tank, but I assume you're going to cut it somehow in order to build your forge.  If you can cut it, you can always cut a portion out to make it shorter, even if you want to keep the rounded ends.   Personally I'm moving away from the rounded ends anyway, but that's a matter of personal preference.  

If you want as easy to tune as an OA torch then a blown burner is the way to go.  Then you can adjust air and fuel as you desire without worrying about jet alignment, tube length, and a few other variables.  You just have to adjust one when you adjust the other to keep the same forge atmosphere and you're tied to power with your blower. 

If the picture I have in my head is accurate then your aiming method should work well.

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The nearest party store I know of is in Nashville, about 70 miles away.  Living in the "sticks"does have some disadvantages but I wouldn't trade it for those advantages. I have deer and turkey walking through the yard, have a 100 yard rifle range and a 25 yd  pistol range in the back yard and no zoning regs to worry about. Does make acquiring some things more difficult, but Amazon fills in many blanks. One of the other things about a longer chamber is that I plan on eventually trying some Damascus and I figured the extra depth might be helpful there. Of course I may be on my 2nd or 3rd forge by then. I have been having a ball playing with mild steel and my charcoal forge. So much so that I can see becoming hooked on it. I have read several posts about practicing with cheap iron and Tractor Supply and Ace are close by, about 11 miles.  Being disabled and forced to retire I really need something to keep mind and hands busy.

Also, I have thought about using my wrap-around and slicing a few inches off the tank, just not sure if it is worth the trouble.

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If it's too large you won't want to use it. It would be like driving a monster truck as an everyday driver.   Nothing wrong with driving a gas hog but do you want 10 mpg or 3gpm.   In my helium tank forge which is the smallest size helium tank I can heat 12" to welding heat and close to 14" to forge temp. Pretty difficult to work that long of a heat even on my best day. At welding temps my one 3/4" burner will burn a gal and hour. And tank freeze up is a battle with my 7 gal tank.    One 3/4" burner will heat 350ci of forge volume to welding heat.  I don't rem er the size air tank you mentioned but most the tanks I have laying around (7gal)

would need 2 burners

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The tank is a 10"x20", which I figured would give me a 5"x15" chamber after  insulation. Maybe slightly less if I end up building up the floor a little extra. But ya'll have convinced me, I will slice an extra 3" off the length. I am sure the "ring" will come in handy for something. I saw a rig someone was selling to run 2 #20 tanks in tandem. Is this a worth while investment to prevent freezing?

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Wow, I had been considering a larger tank at the appropriate time, but you just made me think about the logistics of moving it and going or refills. With all my back problems it would be much better for me to stick with the 20# tanks. Thank you for the insight. Sometimes the obvious eludes me so easily, LOL.

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Hey Guys,

    New here at IFI and new to forging. I've been playing around with a coal forge that I built from an old fire pump housing and bounce house pump for the past couple of months.  I just recently almost finished a pair of tongs with it in the snow because I'm tired of burning my fingers off with the channel locks.  Other than that, I just like pounding on hot metal.  It's become an obsession and is quite therapeutic.  I have a pile of RR metal sitting on my garage floor that have been pounded flat and almost resemble something of a knife blade but left to rust because there's no pounding left. 

I plan on building me the gas forge in the future so I've read this thread over the past two days from front to back and then when I got done I went back a couple of times because I had gotten so consumed in it that I forgot to take notes.  I especially enjoyed the piece on "What is Art?".

My original plan before reading was to use a propane tank and 3/4 burner.  Now I plan to use freon tank with 1/2 burner.  Will the length of the nipple remain the same or be shorter due to smaller pipe?  I know this a burner ? but literally been reading this thread for the past 7 hours (Slow day at work) so too dizzy trying to get my head wrapped around all the information to read the 35 pages of burners 101 right now.  I feel like I've known you guys forever already.  Thanks for everything that you do!   

 

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You can simply look at the "T" burner threads and build a perfectly adequate burner from that. I do not recommend going through Burners 101 as a first step in deciding how to heat a forge. Build a simple little forge first, and take your time going through that rather large thread at your leisure. One of the sad misconceptions about burners is that you won't make several; you will. 

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I like to show new forges with something outstanding about them, so here is my latest find; an outstandingly bad deal:

https://www.amazon.com/Handy-Forge/dp/B018WLH9JS/ref=sr_1_2?ie=UTF8&qid=1514574700&sr=8-2&keywords=black+smith+forge

Why bring it up? For that much money, newbies could actually buy a real beginner's gas forge from eBay. To add insult to injury you have to buy a torch to run it with, because it is sold without any burner; it is so small that it makes a coffee-can forge look huge; it is made with highly friable insulating firebrick, so you don't have to wait for heat damage to start turning  the "firebrick" into rubble, because shipping will start the job for you.

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Naw, jewelers would laugh. A couple few soft bricks and a hydrogen torch pretty covers it unless they need to cast gang molds. 

Just another example of someone with no experience's "revolutionary new idea" trying to make a buck off the suckers.

Frosty The Lucky.

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Cutting ceramic blanket right for tunnel forges

The formula for finding the area of a circle is plastered all over the Web, including calculators, so what can so many people find jittery about it?  I think it is the fear of cutting a relatively expensive product wrong the first time and having to patch it together. This nonproblem comes from ignorance of three facts:

(1) You don't want to try for a perfect matchup in the first place. Ceramic fiber blanket is springy; you want to cut it oversize so that it must be compressed to fit in place.

(2) If you have a brain in your head you will rigidize the blanket once it is in place, which will also glue together any patches you may have in the material.

(3) The last thing you do is plaster a seal coat over the blanket, so any leftover seams will disappear anyway.

So what is there to get uptight about?

 

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  • 2 weeks later...

I have always maintained that if I was the smartest guy in the room, I was in the wrong room. Not much chance of that in here. 

I presently own an ABANA forge that I build a couple of months after Dirt was invented, 20 years give or take and I am thinking of relining it and at the same time I would like to build something non recuperative. 

The ABANA has 1" 2100° fiber board and some type of high alumina coating on floor and walls, the coating is in pretty sad shape and it was never rigidized. I have a thermocouple temp gauge installed and I have never gotten it over 2100 °. I have managed to weld in it but it has been challenging. 

the new project I am considering is capable of welding, about 600-700 cubic inches with two 3/4" t burners. a square forge about 8"x8"x10"tall is what I have in mind,  I have a supply of 1" dura board LD rated 2300° . I am thinking the fumed silica rigidizer and high alumina coating.  I am wondering about the IR coating, is it really necessary? I can see using two of those little jars which is a fair piece of change. 

the issue of chamber height and is of concern and if the t burner ,being a soft burner, will need more than 10" to complete combustion. I am wondering if the straight vertical burner mount is the best plan of if I need to tilt them or maybe even come in from the side. 

I know this is a bit long and I have just spent a couple days reading and digesting this and the T burner thread and I really need to talk to someone about what I think i learned.

 

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Back about six pages is a discussion of a homemade heat reflecting seal coat, which I would recommend hands down over ITC-100; it costs a whole lot less too.

While I fully back silicate rigidizer for ceramic blanket, I'm less sure about its efficacy on ceramic board.

Two 3/4" T burners should handle the job.

 Proper soft flames generally take less distance than hard flames to finish combustion; I recommend Frosty's burners over my own in square forges for that reason.

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