Help for a Gas Sword Oven / Large Vertical Forge?

[BlackthornForge]

Hi,

I'm looking to build a 72 inch vertical forge with minimal volume.  Does anyone have any advice on design?

 

My basic plan is to use a steel pipe (8 inch diameter) lined with 2 inches of Kaowool.  This will provide a 4 inch diameter mouth that runs the length of the pipe, which will give me enough room to hang longer pieces for a heat treat soak.  I'm not looking for forging heat, but definitely need to get thicker steel to critical temperature for heat treat.  I'm thinking about using a 3-burner system, evenly spaced along the length of the pipe to try to keep my heat even but I'm concerned that I'll end up with nasty hot spots around the burners.  Is there a way to even out the heat better?  Is 2 inches of Kaowool enough to provide efficient operation?  Any and all advice is welcome!

 

Thanks!

[LastRonin]

I am not experienced enough to say with certainty, but from what I have read... I would think ribbon burner(s) would be the way to go if you absolutely want to go gas heated. My understanding is also that burners are harder to maintain steady heats for durations that some steels require. Have you looked into electric? 

[Steve Sells]

Don Fogg has a system of a pipe mounted in a drum in its side, the pipe is mounted at the top of the drum,  the burner is at bottom heating the air, so  its not a forge, but a oven. heating the pipe that contains the blade for even heat.   I can not imagine how many claymores you do, to need a 72 inch oven, not how a vertical manages even heat......

[Michael Cochran]

I've never seen anything that needed a 6' oven . I have a claymore at home an the important bits would've fit  would've fit in a 5' with room to spare.

[Charles R. Stevens]

We have had the same question come up befor this month, and the poster became "upset" with our advice. So understand if we are a bit loath to answer.

for anealing, normalizing and hardening we need a forge/oven that can heat the entire blade ( tho by moving back and forth a foot shy will do) but to forge you anly need to heat 6" at a time as you can't effectibely hand forge more.

[timgunn1962]

First thing to say is that I have not built a sword-length HT forge myself, so bear this in mind if (when) you get conflicting advice.

Don't Fogg came op with a design for an affordable horizontal drum forge built from a standard drum (55 US gall/45 imp gall/200 litres), lined with 1" of kaowool blanket and heated with a small and simple burner.

I am pretty sure the large volume is a significant factor in the even heating it provides.

I have tried to build a scaled-down version with some success. Mine have been built with a 10" pipe shell and a 1/2" burner.

I don't think I'd want to go smaller than an 8" ID, especially if increasing the length to 6'. I'd be looking to put 2" of kaowool lining in a 12-14" shell and use a 3/4" or 1" burner for something that long.

I'd avoid multiple burners like the plague: balancing multiple burners to give exactly the same flame temperature is a hassle I could happily do without. At HT temperatures, the heat input needed is not all that high.

The clever bit is the burner. I use a commercial Venturi mixer made in the UK, but expect something very similar is available over the pond. Otherwise a blown burner would probably give fine enough mixture control. The important thing is that the air:fuel mixture must be very finely and progressively adjustable. My limited experience of homebuilthomebuilt Naturally Aspirated burners has been that the mixture control is pretty much an afterthought and that controlling temperature to within a degree or two of target is frustratingly difficult.

 

 

[Charles R. Stevens]

I would suggest atleast 2" of insulation, and with somthing where temp stability is an isue, soft firebrick may trump koawool as it has more mass (perhaps an inch of koawool oround the brick) burner desighn has a lot to do with adjustability, some like used by Ron Reil are hard to adjust be because they operate under such a nerrow window, wile "T" burners and side arm burners once dialed in for max effecency can use chokes to adust attmaspher and presure to adust temp. With a bit of mass in your oven to stabilize tthe temp you should be ok. But frankly after all the work to produce a blade, particularly a greatsword out of an advanced steel that takes long presise soke times why not send it out? Heat treat shoos not only can control time and temp but also can cotrole the atmasphers, not just to excude O2, but other elimental gasses as well. For "simple steels" a complicated oven isnt at all nessisary. As nicely and Steve may show you his forge. And judging from the handfull of long blades in his shop (including a claymore in his livingroom) i suspect he might know a thing or two about forgin and heattreatng sword blades. We are talking abiut sword blades, right? Or are we making truck springs?

[BlackthornForge]

Thank you all for the advice!  Basically what I'm hearing is:  5' is probably enough, I should build an oven not a forge, and it may be better to send it out.

LastRonin:  I haven't considered electric because I don't have access to good circuitry and I'm concerned about blowing fuses.

Charles:  do you have any good leads on inexpensive heat treat for big pieces?  The only place I know of costs $200 plus shipping there and back, which would be another $100 for the great sword I'm building.

[Charles R. Stevens]

As your looking at a peice that would cost you $3,000+ to have some one forge for you, $ 300 dosn't sound at all unresnabel. But if its a simple steel (say 4060 from a spring shop) then a long trench forge loke a giant wastub forge will work. Steve Sells uses a simular set up with success. Then a temluting oven is cheaper to build. Infact after the inisial temper you can use a torch or large chucnk of hot steel to further temper the center of the blade and the tang 

[BlackthornForge]

Definitely didn't realize a hand forged great sword would run 3 grand!!  I'm using 5160, so it would probably be better to send it out.  Sigh. One day I'll get a proper heat treat setup.

[Charles R. Stevens]

There are only a 1/2 dozzen or so smiths building "real" swards in the US. 

Ask Steve for a ball park, I bet I'm under. 

But remember that the folks who made the originals used faily simply setups, they didnt have thermostaticaly controled heat treat ovens, they had forges and furnaces fueld bu charcoal and later coal. 

Your jumping off in the deap end. Might I suggest starting oit with a dirk first? Mabe a bullock dagger? Their is a huge amount to learn, even if your planning to do this all with stock removal, to make a usable sword you have to understand some things like vibration nodes (where vibrations consintrate when you hit somthing with a hard steel bar) and balace. Much less how thin to make the blade, and how to make it as lite as posible. Make it wrong and it will literaly refuse to stay in your hands, right and you will think it is held in by magic. 

[Charles R. Stevens]

Dont take this as discoragement, you seem to have a good atitude and a sharp mind, this being your ultiment goal will encorage you will you aquire the skills to desighn and build this bad boy!

[BlackthornForge]

I've been making knives using stock removal for about 13 years and got into real smithing about 6 years ago, so I've got a good base as far as technique goes but I've never made anything longer than a machete.  All the tips you have been giving me are great!

[DanielC]

There's quite a few sword smiths on Don Foggs site. More than a dozen. Off topic, but yea there's a few. Swords go for thousands. A lot of work involved and s lot that can go wrong.

[Charles R. Stevens]

Thanks for the corection ;-)

[j.w.s.]

As someone who does this for a living, let me say that when we used to send our swords out for heat treat it was $500 just for setup and $2/lb. Most places that can heat treat aren't equipped with equipment to do large pieces, so you're limited on where you can take it. The longest sword I've done to date is 6'11" from tip to pommel and it weighs in just shy of 11lbs - if you're just trying to do a single piece it's a little cost prohibitive to pay $522 just to have a piece hardened and tempered. It really only made sense for us because we were doing 200+ swords per run so we got the price down to about $5.80 a piece if I recall correctly and we'd do a few runs each year but it's still an expense we didn't need so I built our first heat treat oven, vertical and capable of accepting 48" long blades. It was 240vac and controlled by a PID/thermocouple, capable of reaching 2100F but it really wasn't the best design and poorly insulated to boot. Our current heat treat oven is horizontal, with an opening 13"x11"x60" deep - it also doubles as a forge capable of hitting welding heat over the entire 5ft length and in winter it does triple duty by being our shops furnace - 15 minutes on and we're opening doors. Here's a picture of it right before I finished construction, it's the behemoth in the corner of the shop - made of 310lbs of I-beam, about 100lbs of refractory cement and better than half a roll of kaowool.

-J

[DanielC]

Sweet xxxxxxx oven man.

[Frosty]

Welcome aboard Blackthorne forge guy, glad to have you. If you'll put your general location in the header you might be surprised how many of the IFI gang live within visiting distance.

While 5160 is pretty forgiving of mistakes in heat treat the longer the blade the more critical even little things get.

If you use a gun and ribbon burner in a Fogg type oven you can probably find controls to keep pretty exact temp and ramp times. A ribbon can be as long as the oven but it needs to be manifolded to keep the flames even.

Another thought from a guy who doesn't do this sort of thing is about even heat in the blade chamber (pipe). While iron pipe has a high thermal mass iron doesn't conduct heat terribly well or we couldn't hold a 18" bar and forge the 4" on the end. However we aren't talking really high temps so perhaps the pipe could be copper. A copper chamber would eliminate the need for near exact uniformity in the fire chamber and copper has a melting temp near 2,000f.

Maybe, hmmmm?

Frosty The Lucky.

[BlackthornForge]

I hadn't thought about using copper, Frosty.  Good idea!  Still I might just stick with Charles' advice to send it out.

 

JWS, xxxxxx that's a neat piece.  I won't be doing production runs, most likely, so building something like you guys had is way more than I need, but wow!!!

[Frosty]

Before you start experimenting with my NON EXPERT ideas you might wait to hear from the pros or even see if they give it a try and their evaluation.

Frosty The Lucky.

[Steve Sells]

Just to clarify a comment I made to Charles when he was over here a few weeks ago.  I was talking about one of my first Viking sword commission I had years ago.  I still have the sword the client backed out of, un-paid for to remind me too.  I had told Charles there were maybe 8 people making usable historical reproduction swords in the USA, and the guy that screwed me was surprised when the other guy that he hired for the same blade after I started, asked for 100% payment a month later.    When he asked why he said we mostly all know each other, and after finding out by chance that he had dropped a job on me for $100 lower price, wanted to protect himself.  It is not cool to mess over smiths and still take bids after you already hired someone else to do that job.  I would not take him back, so it was fine with me that the other guy did, but that was to explain why I, and some others, demand a non-refundable deposit before starting custom jobs any more.

I was talking about back then, and not about today nor did I include general sword makers in that statement.  I thought I had better post because PM's are broken, and I can see poor Charles wondering if he messed up the numbers I gave him...

[Charles R. Stevens]

Na, Steve I'm all good! Between your numbers and an informal count of the smiths that have posted good work here I wasn't worring about the correction. Besides I could have been wrong in remebering what you said. I think this guy cound benifit from seeing your heat treat setup for "simple" steel long blades. 

If I was 10 years younger and had the coin I would buy that "reminder";-) 

Edited June 22, 2015 by Charles R. Stevens

[Johnathan T]

I don't know if I should start a new thread, but if I did, it would be about the same thing, so I guess I should put it here. I have nearly the same problem. My current forge limits the length of blades I can make, so I'm looking to get something to allow me to heat treat longer blades. I tried to build something, but it didn't work out well enough. I want to try again, and I wanted to run it by you guys for corrections/answers/advice/criticism so I make something that actually works and I don't end up wasting time and money again. I've done a lot of reading on the forum and have seen what kinds of things you know, so I thought you guys would be the kind of people I would want to ask. This is more of an oven than a forge, but I think some of the ideas still carry over. I've taken time to look around and read, and I think I've come to a conclusion. I also recently finished a commission and decided to use the money earned to help fund this project, so I'm not looking for the cheapest possible option, but I still have a limit.

I understand that an electric oven or salt bath is ideal to heat treat swords, but those are far outside my budget. There is also the trench method, I would like something more permanent. More importantly, a hot sword blade held horizontally bends from its own weight and length, and it would be nice if I didn't have to worry about that. I think it would either need a flat surface or held vertically. Even if it was on a flat surface, it would still be moved out of the forge and into the quench tank. It may also be difficult to make a surface uniformly flat enough. For these reasons I believe I would prefer a vertical propane forge/oven.

I first saw it in this video. I later saw it in this video, this video, this video and in this thread. I plan to make it simple, like in the first video. I just want it to get sword blades up to temperature for normalizing and the quench, if it can temper them too, it's a nice bonus. To control the temperature, I turn the regulator up and down. To see what temperature the blade is, I use an IR laser thermometer. This size will work for most of the swords I make, and when I make longswords, I will tack weld a pipe to the top to get that extra length needed. I don't plan on making anything longer than the average longsword for a long time. I plan to keep working with simpler steels like 5160 for a while. I'll probably store this near the door of my shop and take it outside to use it.

I called around to look for scrap 100lb propane tanks, but all the local scrap yards only buy scrap, not sell it. The welding gas supplier didn't have any. I didn't find any on Craigslist and the like. I might just go to menards and buy one new. Would I need to worry about it having a little bit of fuel in it? I would think that if I buy it new it would be completely empty. I might hook up a forge burner and burn any gas that comes out, and then do what he did in the video, unscrew the fitting, and throw a lit piece of paper to light any remaining gas. I don't have a bandsaw, but I do have an angle grinder. I would cut about 2 inches below the top. 

I think I should use 2 inches of kaowool, but I've heard that 1 might be enough. 2 kaowool circles fill the bottom, the kaowool walls sit on top. If the cylinder is about 15" in diameter, the circumference is about 47". Kaowool comes 24" wide. I could either make 2 full circles that are half the height, or 2 half circles that are the full height. I could be overcomplicating things, but I think it would be be good to put the seams in different places for each layer. For the 2 full circles at half height, the other layer could be 2 quarter height pieces with a half height piece in the middle. For 2 full height half circles, one layer would be rotated relative to the other. I think the 2 full height half circles would be easier. There's also the possibility of a single 2 inch layer, but then I wouldn't be able to offset the seams, but that might not be a problem. The lid would be like the bottom, but it would have a hole going through it. I think there doesn't need to be anything to hold the kaowool in the lid in place, I might tack weld the lid back on the main body once the insulation is in place. When working with kaowool I'll use gloves and my respirator/face shield combo. I want to be on the safer side, and I assume that if I were to not seal the kaowool I would want to wear my respirator/face shield combo, but it would be nice if I didn't have to, so I think I would want to use rigidizer. Should I use rigidizer between layers and on exposed kaowool or just the exposed kaowool? I would guess that doing just the exposed kaowool might be enough to seal the fibers, and rigidizing in between layers would help hold things together. With how tall it is, I wouldn't be able to apply the rigidizer when the kaowool is in the shell. Could I apply rigidizer onto the cut pieces and then put them into the shell? Since this is more of an oven than a forge, I don't think it needs castable refractory. Would this benefit from a kiln wash/IR "reflector"? Even if it does, I don't see how I would be able to apply it once the kaowool is rigidized because it's to long to reach into.

I have a burner from the failed project. The inner diameter of the mixing tube is 1.25". It's naturally aspirated, with a disk on a screw to adjust the air inlet. I bought it on ebay. I think the burner I have is bigger than what's usually used for something like this. If the burner I have will work okay for this, I'll use it, but if a different burner would be far better, I'll buy a new burner better suited to this application, as long as it's within the budget. I'd probably spend at most about $150 on aburner, but I'd prefer something more like $50-100. I think the burner will be installed a couple inches above the bottom of the insulation. I think it should be pointed to the right of center in order to swirl in a circular path, and pointed slightly upward to help form a tight helical coil shaped path.

I have a coal forge, but I've been wanting to switch to propane due to its convenience and because my coal forge has a few things that aren't ideal for my application. I plan to make a forge like in Wayne Coe's "Build a gas forge" instructions. I need the heat treating oven for my next project and many to come, but I can use the coal forge until I build the propane forge. Though it does occur to me that maybe I should build the forge before I build the oven in order to get experience with something small before I make something big. Though I have worked with kaowool and Kast O'lite 30 before for the failed project. I thought I'd bring that up in case it was a good idea.

[Mikey98118]

On 6/19/2015 at 6:25 AM, BlackthornForge said:

Definitely didn't realize a hand forged great sword would run 3 grand!!  I'm using 5160, so it would probably be better to send it out.  Sigh. One day I'll get a proper heat treat setup.

It sounds like you could build the forge you need for about what it would cost to send just one for heat treat .

You probably will need to  make a forge with a very long single row built in ribbon burner, or a fan=blown burner, to avoid back pressure problems.

Because you will only be taking it up to red heat most of the time you can get away with a little less insulation than we usually like to see, so I would suggest a thicker layer of Kast-O-lite 30 semi-insulating refractory. This will stand up better to physical damage than a thin refractory layer surrounded by blanket insulation.

A solid hard refractory should allow you to build a clam shell forge, which will be a whole lot easier to move long material in and out of, without miss-hap