I’m going to post about this project as it assembles itself, to remember what I did, and/or what I was thinking at the time. So, it’s going to be kind of self-referential and possibly contain bad sketches.
Feel free to chime in with suggestions. If you want to suggest, I hate to say this but: suggest in advance of where I am, because if I am posting what I am doing, that generally will mean I’ve already done it or sourced the materials. Sorry about that, it’s just how things work out in project land. On the other hand, this may not be the last forge I ever build, so any and all hints are good. As I said above, I may turn this into a build plan or video, and if there’s a point where I can say “do as I suggest, not as I did” that’s fine.
This is what I currently have:
It’s based on an idea I saw someone do on youtube, [essential]. The idea was pretty much what it looks like: can you build a cheap and easy forge where the forge’s refractory and frame are all there is, plus some burners? It’s the exact opposite of my gigantic overkill forge, with all its overkill thermal mass. This one is built of what blacksmiths sometimes call “soft brick” – foamy lightweight refractory – as opposed to “hard brick” which is what covers the table-top it is standing on. In fact, that hard brick is going to make up the frame of the next forge, because I’ve learned a bunch of stuff from the current forge. There are places where I invested effort that was wasted, and a few where I did not. But it has been a great hard-worker for me, and comes up to welding temperature in about 10 minutes, which is spectacular.
As you can see it’s built from 4 pieces of L-bracket (I have a lot of L-bracket in my steel scrap pile) and some 1/2″ID square steel tube and some allthread and washers and wingnuts. There is a steel plate along the bottom, which is pinched between the square tubes and the L-bracket, and is the size reference for the entire thing. That is it!
From the other side:
I made a big heat deflector/hand protector on the burner side, because I thought that might be Smart(tm). It turned out to be unnecessary, entirely. The soft brick is so insulating that you can put your bare hand, with some trepidation, on it while the forge is at welding temperature. I mean “put your bare hand on it, and pull it off again, undamaged.” Gaps eventually form between the bricks from oxidation, but in this build they are not too bad of a problem unless you’re putting your bare hand on the forge and put it over one of the gaps. The deflector is mounted on 4 pieces of the square tubing, with bolts coming through from the back, supported by the burner mount, which you cannot see. The burner mount is just a piece of 2″ steel 1/8″ bar that is screwed into the square tube uprights, has holes in it, and serves to support the burners. As you can see, the other thing supporting the burners is the heat deflector, and the burners are wired in place with steel wire. I have seen what happens when a burner shakes loose and decides to go walk-about. Make sure your burners are really solidly attached to something.
We’ll look at gas distribution systems in a couple episodes but spoilers: the red thing is the regulator. On the other side of the regulator is a ball valve (spray painted red), a quick release propane coupler, and the hose that runs to the propane tank. There is another ball valve and quick release on the wall, and a cutoff valve outside on the tank. If I need to, I can disconnect the hose, run it outside, and connect it to the quick release connector on my smelter or anything else that wants to run propane.
If you look carefully at the pictures of the forge you can see that eventually thermal cycling got the better of the soft brick. The hard brick is fine, but I assembled the soft bricks into a sort of air-tight mass by sawing and lapping them, to get the exact interior size I wanted. … All of which brings me to a point: the current forge is too short, and to big for what I mostly do. Sure, it is great to have lots of space but mostly I am working on things that are 3″x3″x6″ to 12″ long. [By the way, Trump says that when he is inaugurated, we are going to put a tariff on any country that does not use “freedom units” which are based on the foot size of the very English monarchs we went to so much trouble to get rid of.] Lately I have broken my treaty with myself, to mostly make cooking implements and useful things, and have been making the most evil flesh-rending pieces of cruelty that I can. For that the existing forge is too short and could easily be half the interior dimension.
New design strategy point: I am going to use hard brick plus ceramic felt cloth, and will not be cutting or adjusting brick sizes because it is painful and breathing dust from refractory is bad. The old one’s interior was parged with satanite and infrared reflector, and I will repeat that in this design as well.
New design strategy point: Instead of the small 1/2″ID square tube I am going to use 1″ square tube. There’s a reason for that, which is that I can also drill crosswise through the tube and have enough room to put 1/4″ allthread or bolts through it. When I mounted the burner bracket, I had some fiddling to do to get the screws in without hitting the vertical allthread. So I will use something a bit bigger, which will also be more sturdy since it’ll have a larger cross-section at the top and bottom.
New design strategy point: The old forge has a “roof” made by spanning the top with bricks. To do that I had to table-saw soft brick and make the sides come in enough to support it. The old roof is crumbling. The new roof will either be: a) just 2 layers of ceramic felt and some wool on top b) a frame made of L-bracket with 2 layers of ceramic felt stretched across the gap, poured on top with cast-o-lite or mizzou c) a frame made of L-bracket that holds a number of hard bricks sitting on a layer of ceramic felt. The objective of this is to make it very easy to remove the roof, so I can clean inside and/or move a movable baffle that allows me to shorten the inner space if I am not making something long. (see next point)
New design strategy point: The old forge has 2 burners and the back is closed with a pair of hard bricks that sit on an L-bracket that holds them at the right height. That worked remarkably well since I can open or close one of them. But, if I have the forge open at both ends, it loses heat. I really only need length in the final stages of making a katana blade, so I am going to make the new forge a 3-burner forge, where one burner is generally shut down, and there is an interior baffle that shortens the length by moving back and forth inside. Just lift the lid a bit, move the baffle, turn on the 3rd burner, and it’s ready for full length swords. Best wait ’till its below welding temperature before you try to move the interior baffle. I’ll need to put a few thoughts into the overall length I will be working with in a given session.
New design strategy point: I have made a few postings in blacksmith forums about this, and have generally been ignored, which (as I am sure you can guess) annoys the living shit out of me. I called the Chili Forge people and Coal Iron people and talked to their engineers about this and … nothing. OK: flux (borax) if you use it, glassifies quickly and forms an oxygen barrier. But, when it cools it contracts a lot, which is a problem because it has soaked into your bricks. One or two sessions with flux, and your bricks begin to crumble into powder. I was watching one of Everyday Astronaut’s Elon Musk SpaceX worship sessions and got to thinking about exactly what the fuck the afterburner nozzles on an SR-71 are made of. Afterburner nozzles have to handle heat (and lots of it) as well as oxidation (lots and lots) so they have to be made of some crazy stuff. Turns out they’re made of the same stuff as the rocket bell on an X-15. It’s a material called Inconel which is a sort of nickel-chrome-steel alloy that has a melting temperature up in the mid 3000Fs, and oxidizes like stainless steel – some but not very fast. So I made a flux tray out of 16-ga Inconel, thinking it would not be much thermal mass and much to my surprise, it took dozens and dozens of sessions with flux and all that hot gas, before the Inconel started to decay. Since I am making the new forge very well insulated, I don’t think that the additional thermal mass of having a couple pieces of Inconel inside will make much difference. I am going to see if I can put half-height sides in, and a long tray in the bottom, then smaller disposable trays for work. I will polish the inner surfaces of the sides to mirror shine to reflect heat. Who knows? This is experimental and if it doesn’t work, I can go back to hard brick or just cast the bottom full of mizzou.
New design strategy point: There is no “lintel” on the top of the frame, so the whole frame is held square by the square bottoms of the tubes. In retrospect, I could have invested the extra 25″ or whatever of L-bracket. I have lots. The new one will have front and rear lintels and possibly the front lintel will support a sliding door.
One of the great things about the allthread/wingnut/tube steel assembly is that you can assemble the unit loosely, make everything fit, then snug it down. My plans for the sides, for example, involve wrapping ceramic felt around the inside of the vertical hard bricks then letting the L-brackets just hold it in place. No gluing no sewing no lapping or layering.
This is the current state of affairs:
In my supply piles I have washers, wingnuts, allthread, L-bracket, etc. “not shown” here. The bricks represent the total dimensions: 6 vertical hard bricks long and one horizontal hard brick wide. The interior should be roomy but not big enough to turn a cadillac around in. I have overlap so if I want to make the roof loose, I can just drape a piece of ceramic felt over it and hold it down with hard bricks. The bottom will not be as shown – that is just to get the dimensions. The bottom will be a metal plate in place between the bottom L-brackets with some ceramic felt on top of it and then the Inconel tray.
The vertical brick partway down represents the movable interior baffle, which may require cut to fit but ought to be more or less the right size. The burners will go with 2 in the front area and another behind where the interior baffle currently is. If I want to work on something long, the interior baffle can come out or be moved all the way to the end of the tunnel.
Not shown here is a “porch” like I have on the current forge. Wow are those useful! All I did with the old one was extend the bottom L-brackets and put some hard bricks in to get the right height. I will probably extend the L-brackets on the bottom so they are long enough to hold 2 width-wise hard bricks and I’ll trim them if I have to. Or I’ll use an angle grinder to cut away the top of the ‘L’ in the L-bracket so that the hard bricks can just sit right there. The porch is crucial, since it’s where you put things down to change your grip on them, etc.
Another topic I have not touched on is the question of a front door. Having a front door makes a huge difference in heat-up time. I was thinking I could put an L-bracket across the top as a ‘lintel’ of sorts with the ‘L’ edge up and facing out, then make a frame with some pulley wheels that could be casted full of mizzou or cast-o-lite. [Remember: I have a metal lathe] it’d be fun to cast some kind of logo through the door, like some hands doing “goatse” or something but as you can tell I don’t have any good ideas about that yet. Last year I did some experiments with a frame that I put ceramic felt across and cast refractory into, and it works great. You wind up with an insulated refractory that is strengthened by the fibers in the ceramic. It is a great technique and I think making a door would showcase it.
I apologize for dropping postings here, and not interacting with you all as much as I used to. I have become a much slower writer, which makes it hard for me to sit down and hammer out responses to comments in a half hour or so, it becomes a 2 hour project which then means I need a nap. I do not know if this is a normal age thing or a brain injury thing but I have noticed that if I remain still (as in: sitting behind my desk) my eyes drift closed and then I have ruined my chances of sleeping that night.
It has occurred to me that I could easily enough build a ribbon burner. That is well within my capabilities but I am not sure if I actually want to go that route because then I need a pressurized air system and yadda dadda dadda etc. Venturi burners are plenty hot enough and once the fire chamber is up to temperature, everything heats evenly. I guess I am saying I could do it but I might be just showing off. I know you all know I am immune to that particular weakness.
Glad to see you posting again.
Not sure how relevant this is, but as far as swords/long blades, would there be any benefit to getting a masonry/concrete coring bit, and just cutting some holes in the middle of the hard bricks, and making a big stack of them that way. or, if that’s too expensive/difficult/not enough space, cutting some “V” notches in the top/bottom of the hard bricks, and pairing and stacking them to make a tunnel-like forge.
It sounds like you have plenty of space, so would it be worthwhile to build separate forges for specialty purposes?
Otherwise, I’m wondering if there is some sort of clay like material that you could just mold/sculpt, let dry, and fire/heat to make a custom sized/specced forge. maybe whatever they make the hard bricks out of?
at my workplace, one of the people who retired did some welding and blacksmithing and such (not much bladesmithing though, if I remember correctly…), and left a few things behind. I think there is some sort of fire brick, and some fibrous type mineral stuff. no idea what they planned with it, but maybe I can poke around in late January and try and figure out what there is an make some guesses as to why…
This is why spoilsports invented 3-D printing.
Would having a triangular shaped chamber with a floor and 2 leaning walls make sense instead of having a rectangular shape with one horizontal ceiling? It would seem to optimize the used heated volume and avoid a potentially fragile horizontal surface. But I don’t know how fragile the leaning walls would be though.
Lovely to hear you are nearer starting/have started to build this forge, as you’ve mentioned it a time or two.
I’ve nothing useful to add, just an example of the difference between English and American, what you call ‘L-bracket’ we would call ‘angle iron’. Used to use it back in the days when I helped make steps on paths we built through bits of land connecting different parts of Sheffield – they weren’t built on because they were so steep so we invariably had to put in a lot of steps*. Shape the space to receive a sleeper (railway tie?), one person holds it in place, another holds the angle iron against one outer corner of the sleeper with a block of wood on top while the third rams it home with a sledge hammer burying at least a third of the angle iron, repeat with the other outer corner, back fill as necessary behind the sleeper and ram down. Repeat all the way up whatever slope the path was going up until you got to the top. I was pretty fit in those days, and as near having a tan as I can get, which is to say a shade darker than usual
* Sheffield, like an even more famous city, is built on seven hills with seven rivers between them. Some of the slopes were very steep, once all the slightly less steep slopes had been built on people decided they liked the strips of trees separating them from the next district round, so they are now protected.
Inconel is marvelous stuff! Anythng used in a nuclear reactor environment has to be strong, survive high temps, and have crazy corrosion resistance. I understand it can be tough to machine or weld though.
The X-33/VentureStar was also using inconel films ~0.006″ brazed to honeycombs in the two different thermal protection systems that were under development prior to being cancelled because mil projects are always funded with endless delays and cost overruns but civilian projects can never be allowed any waste or failure. NASA will still have the pdf scans of the various development and test papers on their archive for a while longer, but who knows how long that survives.
Another thing I’ve been wondering about as cheap/disposable thermal protection/insulation in forges/kilns is diy starlite. NightHawkInLight tested a bunch of recipes and his ‘final’ version using only grocery store components: 2 parts flour, 1 part corn starch, 1 part borax, 1 part powdered sugar, 1~3 parts water. Mix into a dough and form into shape, then let dry. When it gets heated enough, the heated surface basically expands into a carbon foam like some fire retardant paints/coatings.
That recipe popped back into mind when I stumbled upon ‘filamet’ (>80% metal filled PLA for sintering) a while ago which got me looking at electric kilns again for sintering/brazing, but too many other uncompleted projects as it is. Since the materials are so cheap and available, I am still considering just going on a grocery run and making up a big batch around a form then taking the cheap ‘200,000 BTU’/3500F propane burner to it for a full 20lbs tank.
Pierce R. Butler@#2:
This is why spoilsports invented 3-D printing.
Yes, and no. What’s interesting about 3D printers and CNC machines is that their value is only achieved at scale. If I want 4000 forges or knives, CNC machining them makes sense. If I want 3 forges or knives that are the same, 3D printing might make sense. But generally every thing I make is unique. I have done 3D modeling and printing, and it’s actually much slower than just grabbing a piece of steel or whatever and making it do what I want. Even for some complicated things, it’s easier. In this case, my whole design is based on minimizing the amount of custom stuff I need to do. I’m only getting custom where it amuses me to do so, because sometimes it’s irresistable.
More importantly, I was some form or other of UNIX system administrator from 1983 until a few years ago, and have been a Windows and DOS system administrator since both of those platforms (technically they are 3 platforms but…) crossed my radar screen. When I started, I really enjoyed it. When I went full-time professional system administrator (1985-7) I started to hate it. Imagine my horror as everything computerized and requires system administration: cameras, cars, 3D printers, CAD machines. Every damn thing is updating itself over the internet, all the time. It’s an absolute failure to automate wisely. The idea of using more technology that requires management does not make me happy at all.
Jean@#3:
Would having a triangular shaped chamber with a floor and 2 leaning walls make sense instead of having a rectangular shape with one horizontal ceiling? It would seem to optimize the used heated volume and avoid a potentially fragile horizontal surface. But I don’t know how fragile the leaning walls would be though.
It would probably be good. As you say, you want to minimize the space and maximize the swirl. But here I am trying to avoid having to make forms and molds and cast my own bricks (but I might, for some parts) The idea is to make it as easy as possible and replaceable and disposable so I don’t have to care about it much more.
There is a guy in instagram (Jorgen Harlan) who makes fine art forges that are carefully designed and cast to maximize and perfect heat flow, etc. They must be insanely expensive and they do weigh hundreds and hundreds of pounds. I can’t tell how much he forges at all, but he makes forges.
rrutis1@#5:
Inconel is marvelous stuff! Anythng used in a nuclear reactor environment has to be strong, survive high temps, and have crazy corrosion resistance. I understand it can be tough to machine or weld though.
I think it gets its corrosion resistance the way stainless steel does: it covers itself in a thin layer of oxides that are very tough and inhibit further oxidation. That would be the nickel and chromium in the alloy, I suppose.
Everything that shields itself with oxides can still be welded, but you need to use an inert gas shield, which means you’re basically TIG welding, and I assume the high melt point means it solidifies quickly, too. An expert welder would have no problem with it, but I am not going there.
By the way, update on the status: I have most of the steel cut and ready to start drilling and stacking it. I appear to have mis-measured two pieces and I topped that by leaving them in the wrong place, so I have to wait until I am back from christmas. Then I will post a few more pictures and get into the insulation and rigidization.
I am still undecided about the ceiling. I’ll probably go with pre-cast tiles.
MattP (must mock his crappy brain) @#6:
Another thing I’ve been wondering about as cheap/disposable thermal protection/insulation in forges/kilns is diy starlite. NightHawkInLight tested a bunch of recipes and his ‘final’ version using only grocery store components: 2 parts flour, 1 part corn starch, 1 part borax, 1 part powdered sugar, 1~3 parts water. Mix into a dough and form into shape, then let dry. When it gets heated enough, the heated surface basically expands into a carbon foam like some fire retardant paints/coatings.
That sounds amazing. Certainly nothing fancy. Clever to use borax to self-glassify. I’m not sure I like the expansion. I’ll research that, though, and give it a shot.
I made some cast-o-lite that was 50% styrofoam crush by volume. That worked great, too, but it smelled like sh@t and never stopped smelling like sh@t. Lots of volatile hydrocarbons later…
That recipe popped back into mind when I stumbled upon ‘filamet’ (>80% metal filled PLA for sintering) a while ago which got me looking at electric kilns again for sintering/brazing, but too many other uncompleted projects as it is. Since the materials are so cheap and available, I am still considering just going on a grocery run and making up a big batch around a form then taking the cheap ‘200,000 BTU’/3500F propane burner to it for a full 20lbs tank.
The hardcore wootz makers just stack soft brick, cut a hole for a burner, and let it rip. You might also enjoy looking at what is going on with the use of celluloid, antifreeze, and powdered metal (basically, DIY silver-clay) – there are a few people on youtube making damascus by rolling it out and twisting it with a rolling pin then baking it in the forge. There are also a few people making PLA/metal shapes that fuse into powdered metal, then sintering them in a canister. Basically, it brings 3D printed forge welded patterns into existence.
I don’t know if its my age or brain damage but I feel like I can’t handle the complexity of some of these processes and I am quite happy to just hot-fold and twist low layer-count stuff.
lochaber@#1:
Not sure how relevant this is, but as far as swords/long blades, would there be any benefit to getting a masonry/concrete coring bit, and just cutting some holes in the middle of the hard bricks, and making a big stack of them that way. or, if that’s too expensive/difficult/not enough space, cutting some “V” notches in the top/bottom of the hard bricks, and pairing and stacking them to make a tunnel-like forge.
I think most bladesmith’s (self included) attitude is going to be “it’s just gonna take more propane” – if I really wanted amazing insulation I could just stack a tunnel of soft brick – giving me about a 3″ gap – and stick a burner in the end. It would be efficient, but awkward. What we need is something that has room for work, and is solid enough to take a few bangs and bumps, does not weigh a ton or cost as much as even a small boat. My old soft brick forge is very, very good for a forge, but it is not as tough as I’d like it to be, so I’m giving up some insulation for more durable brick. I could use other things than brick, but then there’s cost and weight.
One blacksmith I know keeps pointing out that a smallish forge made of 5 or 6 pieces of aerogel would be fine. Or carbon/carbon foam like the tiles on a space shuttle (I know for a fact the leading edge pieces cost $250,000 apiece because they had to be cast precisely and then CNC machined to perfect tolerance) And there’s only one thing that can machine carbon.
It sounds like you have plenty of space, so would it be worthwhile to build separate forges for specialty purposes?
You are correct that space is not a problem. I actually have 2 commercial forges stacked in a closet… The problem is that the damn things are either heavy, awkward, expensive, or toxic and sometimes all of the above. Usually you emplace them and use them until you decomission them. With my current design, if I am doing knives instead of swords, I just lift the lid, move the interior baffle, and shut off the gas to the third burner. I just can’t shift gears with the engine running.
Otherwise, I’m wondering if there is some sort of clay like material that you could just mold/sculpt, let dry, and fire/heat to make a custom sized/specced forge. maybe whatever they make the hard bricks out of?
Yes, there are 2 main refractory cements: cast-o-lite, and mizzou. They are approximately the same: fireclay, portland cement, fiber-ceramic, and alumina. Cast-o-lite has pearlite ground up in it, and when it sets up and you heat it the pearlite turns to glass lined voids, which are actually pretty great. I have 15 50-lb sacks of mizzou and I consider that a lifetime supply. I could make forms and mix cement and cast it, but the object of this project is to make it relatively easy. My current foam brick forge took about a day to build. The new one will take less than that since I am thinking ahead and won’t be fudging the design as I go.
I think there is some sort of fire brick, and some fibrous type mineral stuff. no idea what they planned with it
Why not just leave that stuff alone? Really. The fibrous stuff is almost certainly kao-wool, AKA ceramic fiber, AKA guaranteed lung cancer. It’s right up there with asbestos. It’s used as a strengthener in most refractory, which is why cast-o-lite and mizzou have warning labels on them that are really, seriously, intimidating: “THIS PRODUCT WILL CAUSE CANCER” ummm…. didn’t you mean “maybe”? When I work with it I stay upwind and wear a chem mask and throw my clothes away when I am done. It is SO FUN to work with in the summer when it’s hot.
jazzlet@#4:
what you call ‘L-bracket’ we would call ‘angle iron’
I picked the nomenclature up from an old friend who calls it “V-bracket” if it’s not oriented on 90 degrees, and “L-bracket” if it is. “Angle iron” is the correct name for it, but – what angle? I wanna know the angle! Fred and I used to build stuff together sometimes and it turned out that saying “hand me the V-bracket” conveyed enough design information from the orientation that you knew which piece was being referred to.
Shape the space to receive a sleeper (railway tie?), one person holds it in place, another holds the angle iron against one outer corner of the sleeper with a block of wood on top while the third rams it home with a sledge hammer burying at least a third of the angle iron, repeat with the other outer corner, back fill as necessary behind the sleeper and ram down. Repeat all the way up whatever slope the path was going up until you got to the top. I was pretty fit in those days, and as near having a tan as I can get, which is to say a shade darker than usual
I’m going to be pedantic and say I hope that by “angle iron” you mean mild steel. Because actual iron implies pre-bessemer refinement and it’s probably puddle iron, or wrought iron, and people like me will appear late and night and try to pull them up and run off with them. I actually bought several sections of graveyard fence, which amounts to a lifetime supply (especially since I nearly killed myself shifting it) and then there’s my west coast friend who went to visit an old machine shop that was being shut down, and he asked them if they had any wrought iron and the guy said “help yourself” and there were whole chunks of plate and I-beams sitting in a heap under some bushes, where they had been sitting since 1919.
Out here in Pennsylvania there are a lot of railroad tracks coming into and going out of repair, so railroad ties are easy to come by. You just have to, you know, move them. The way we do stairs here is a couple of 6 foot pieces of mild steel “rebar” (crap steel) hammered down through holes drilled in the wood. And then there was my ex-wife whose idea of a great alternative was river rocks. Big ones. The bed of my old farm truck was pretty rusty and hauling tons of rock made it come apart.
I recently got an electronic infrared thermometer that has a surface temperature mode. It doesn’t have that much of a range (anything less than 0C/32F is “Lo”, anything more than 60C/140F is “Hi”), but that’s more than good enough to tell if “safely put your hand on it” is warranted before actually putting your hand on it. There are better thermometers out there with greater range.
Of course, this may just be recency/personal experience illusion, and everyone who works with stuff at extreme temperatures already has an infrared thermometer. Oh well.
Owlmirror@#14:
I recently got an electronic infrared thermometer that has a surface temperature mode. It doesn’t have that much of a range (anything less than 0C/32F is “Lo”, anything more than 60C/140F is “Hi”), but that’s more than good enough to tell if “safely put your hand on it” is warranted before actually putting your hand on it.
When I started working with hot stuff, I made up a little squirt bottle full of water and carried it in the front pocket of my apron. Until I learned to subconsciously time all the cooldowns of the various things around me, I’d just squirt a bit of water on something before I touched it. After a few times when it blasted into steam, I figured out where heat transfer was a problem, and the slow way appears to be my favorite mode of learning.
I also have a laser indicated infrared thermometer, which is pretty good as far as those things go, but I can’t get accurate enough readings to tell which side of melting temperature I am on. Very frustrating.
Update: tomorrow I will be doing some bolting together