Forges 101

[Mikey98118]

I think other voices are important for folks to hear.  Also, you went into providing an insulated base, for the pile to set on, further than I did.

[Davidkinlaw]

I found a of 4mm thick sprinkler pipe about 22cm in diameter and about 50 cm tall for a gas forge. I plan on lining it with wool and then refracturary cement. My question is could I use mineral wool or does it have to be ceramik wool? 

[ThomasPowers]

What is the temperature limits for the exact type of mineral wool you are looking at?  (But in general the answer will be NO! And PLEASE avoid asbestos!)

[Davidkinlaw]

The mineral wool is rated at 1000 Celsius. I was maybe thinking the refractory cement would absorb most of the heat and would affect the mineral wool that much. 

[Mikey98118]

That comes to 1832 degree Fahrenheit. Perlite is good to 1900 F, and costs very little in the garden department of large hardware stores; it still isn't able to hold up as the primary layer of insulation. However, you could use either one as the secondary layer outside of a primary layer of ceramic wool blanket. There are various sources that sell this product by the square foot; by halving the amount of it needed as the primary insulation, it should become affordable.

[Mikey98118]

Perlite is usually "glued" together with sodium silicate to form a solid secondary insulating layer, or is used as an insulating ingredient in castable refractory, much the same way sawdust used to be, before home builders wised up; nothing prevents it from being packed and trapped into a confined area, where i it can support considerable weight above it, so long it it is spread out.

Three kinds of gas forge fall into the knife making category: Coffee-can; half muffler; or Freon/helium tank. The first forge is only chosen by people who are looking to keep cost down as their only concern; the second kind is used for people wanting the maximum use out of a small tool; Use of a two gallon Freon or helium cylinder is the choice of people wanting a lot of use for a minimum of effort. That effort begins with how easy they are to obtain, because both kind of cylinder is non-refillable; so those they can't give away they have to pay to get rid of. Finding and prepping your equipment's steel shell is a fine use of your time, while you are learning how to put the rest of the forge together.

[Mikey98118]

 

 

 Miniature Heating Equipment

    It has often been brought up that about $50 is what many guys feel to be the limit of their budget, to decide if they want to get into hot work as a hobby; that isn't going to get anyone vary far, but if you're careful it will get you started. The good news is that you can always upgrade from your humble beginnings, just so long as you keep that goal in mind from the very first step.      

With a coffee-can furnace that would require paying careful attention to the burner port; this is where the burner is connected to the forge shell (the can); it can be done different ways, but I would advise a beginner to use Larry Zoeller's method.

    This combines pipe nipples with lock rings for electrical conduit (which uses tapered pipe thread) to build steel burner ports. You can use this for various burner sizes. The same thread size that holds your MIG contact tip in a burner can be used in a single or double ring of three bolts each, to hold your burner trapped in the larger pipe of the burner port.

    What is less than desirable about this method is the burner must be aimed straight into the forge from its shell, but it is good enough for a beginner’s forge or furnace.

    The one thing to be careful of is where to position the burner port. People crash and burn at this construction stage, by trying to position the burner too soon. What you want to do is to position steel angles or brick between and below the can as temporary stops, so that you can turn the forge in place. You then use the new forge to heat up two 1/8" by 1/2" steel flat bars, and bend the hot bars around the can's exterior, to form partial "U" shapes (only about  ninety degrees instead of 180). Once cooled, bend their ends are bemt back the other way, to form a couple of  lazy "W" shapes, to hold the forge with. Drill holes for sheet metal screws or pop rivets into the forge through in the flat bar, once you know how you want to place them; then put your bit of kiln shelf or refractory floor at the bottom of the forge, after you have been able to decide, the easy way, just where that should be.

    The beauty of this design is that, should you decide not to become a blacksmith, it will still become a useful handy man tool, as it can be employed to shape and harden a multitude of small tools for other craft work and maintenance.

    The single largest expense will be the ceramic fiber insulating blanket, but only if you purchase it. Your local HVAC, furnace, or boiler shops all collect remnants of ceramic blanket that they cannot use (code prevents them from using scraps; they have to employ fresh material from the roll), so they have to pay to have odds and ends of these refractory rolls hauled away. Let them know what you are up to, be friendly, and garbage bags of the stuff could be yours for a box of donuts and a smile. The same rigidizer you use to stiffen ceramic blanket can be used to glue remnants together. If you have to buy it anyway, the added expense of getting 8 lb. density and minim of 2400 °F rating isn’t much:  

Super Wool fiber blanket (continuous use rated for 2,372 F (1,300 °C) for $4 per square foot for 8 lb. density and 1” thick. ($32 minimum order, plus shipping):  

Perlite is usually "glued" together with sodium silicate to form a monolithic (solid) secondary insulating layer, or is used as an insulating ingredient in castable refractory, much the same way sawdust used to be, before home equipment builders wised up; nothing prevents it from being packed and trapped into a confined area, where it can support considerable weight, so long it is spread out.

Colloidal silica rigidizer: The meaning of the term “colloidal” is a material that can stay suspended in water; most minerals, including silica, will do so if its particles are ground small enough. Fumed silica, a very light an economical substance, is colloidal. It is also easily obtained through eBay and Amazon.com. If you have a local pottery supply store, a spritzer topped bottle of rigidizer is a minor expense; otherwise, you are better off to buy fumed silica and mix it into water to make your own rigidizer, rather than paying for shipping. Food coloring is used in the commercial mixtures as a visual aid for seeing how far the silica has penetrated into the ceramic blanket; it then burns out during firing. Do not allow your rigidizer mixture to freeze, or it will be ruined. Colloidal silica rigidizer is use rated to 2300 °F; above that temperature it slowly begins to break down. Bit doesn’t melt below 3000 °F.  

 

Sodium silicate (AKA water glass): This is any of a number of glassy alkaline silicates dissolved in water. How thick the mixture is depends of the amount of solids to water used. Sodium silicate makes an excellent binding and adhesive agent for Perlite; it melts at 1900 °F, which is also Perlite’s melting temperature. Due to its sodium content it forms a mildly caustic base. Rather than heat, carbon dioxide in the air is used to slowly cure the silicate in position, or carbon dioxide, as compressed gas or dry ice, can be used to rapidly solidify it. Because of its use as a sealant for concrete sodium silicate is available from large hardware stores, like Home Depot.    

Three kinds of containers are used as shells for miniature heating equipment: Coffee-can; half muffler; or Freon/helium tank. Coffee-cans are mainly chosen to keep cost down, as the central concern; half a car muffler gives the maximum use out of miniature equipment; two gallon Freon or helium cylinders provide a lot of use for a minimum of effort and expense; that begins with how easy they are to obtain.

    Each kind of cylinder is non-refillable; so what Freon cylinders HVAC contractors, or helium cylinder party stores can't give away, they have to pay to get rid of. Finding and prepping your equipment's steel shell is a fine use of your time, while you are deciding how to put the rest of your forge together. Miniature casting furnaces can be built with either two pound coffee cans, or with Freon/helium cylinders depending strictly on the size of crucible employed. Be sure to be up front about what you want the empty cylinder for, and be friendly.

    The name “coffee-can” is something of a misnomer; these forges are often built from 2 lb. coffee cans, but #10 tin cans, or one gallon paint cans will do just as well. If you choose to employ a coffee can, take care to use the new kind with the plastic lid and foil top, because it features a 1/2" wide rim around its top rim, for the foil to cling to; this keeps the open end of your forge nearly as rigid as the bottom end of the can; paint cans are even better about this feature. The beauty of this design is that, should you decide not to become a blacksmith, it will still become a useful handy man tool, as it can be employed to shape and harden a multitude of small tools for other craft work, and maintenance.

[Charles R. Stevens]

Well, not in Gas, lol. Solid fuel is another mater. 

[Mikey98118]

  First forges

I would suggest that you start with a mini-forge made from a non-refillable helium or Freon cylinder, Commonly used for building a knife maker's forge. These are two-gallon size containers. You could make a half-muffler oval forge, or a "D"  shaped forge in this size range, but there is much less information available about constructing them, and so the Freon or helium cylinder forge is usually recommended to newbies. You can find a pretty complete account of how Ron Reil built his mini-forge on Ron Reil's Burner pages. You can find  step by step instructions on how to build a a five gallon forge by downloading a pirated copy of Gas Burners for Forges, Furnaces, & Kilns, and simply down size the instructions to build a two gallon cylinder and a smaller burner. This will give you plenty of information to read while you're finding and prepping your first forge shell. Free Freon cylinders are available from HVAC dealers, and helium cylinders from party stores.

You will want two 3/8" or one 1/2" burner to heat such a forge; Choose a Frosty "T" burner, a Zoeller "Z" burner, a Mikey burner, or a Reil burner with the MIG tip update.  Forget using an angle grinder for cutting and grinding on the forge. Rotary tools are now available at reasonable prices, and are better suited to working on small parts.

What about a two-brick, or a coffee-can forge instead? I only recommend them for people who want to build and fix hand tools, or as introductory forges for people with cold feet and no commitment beyond cutting costs to the bone. Since free insulation in the form of ceramic fiber scraps can be glued together with with fumed silica in water that is spritzed from a used cleaner bottle, I don't think the savings will be much. Unless you want to occasionally use your burner as a hand torch, the canister mount torches employed by some in two-brick and coffee-can forges are an economic mirage. By spending $20 on a 0 -20 PSI variable regulator, and borrowing your barbecue grill's five gallon propane cylinder, you can outstrip the false economy of fuel canisters in a single morning's use.

[Mikey98118]

Forge/ furnaces: joy, or misery?

In the main, it is true that multitask tooling is problematic. As with so much else, circumstances alters cases; on a case by case basis, gas forges. and crucible furnaces marry much more easily then any other tool I'm familiar with. By keeping the main limits of the design to an outer insulating layer, or layers, with an inner 1/2" thick heat face layer of high temperature refractory, bringing off this trick becomes a matter of details: a very flat inner face on the forge's far wall (I would suggest a round kiln shelf); a hinged near end that can open to move the crucible in and out; additional legs on the forge's far end (or by turning the forge body on an axis), allows it to be turned up for use as a crucible furnace, very easily. The biggest difference you must contend with is burner placement; a shingle burner must be placed near the bottom of a casting furnace for efficiency, while it must be placed in the center of a forge for the same outcome; so here we find a far from insurmountable limitation placed by multidasking; it becomes a question of which task is most efficiently served by such a tool; that is...unless you use two smaller burners. Then, you get to eat your cake and save it too

Now for the not so happy news. If you are pinching pennies, casting is going to involve a complete separate list of expenses: molds, casting sand, a different set of hand tools, and of course crucibles. Fortunately, the term "economies of scale" goes twice for crucible furnaces as for forges; just check out the cost differences in crucibles by size, to understand that SMALL matters for more than fuel costs.

Bottom line is; think small time Freon or helium non-refillable cylinder for your forge/furnace, and save BIG time.

 

[Mikey98118]

 

[Mikey98118]

Above is a link to, among other things, is a picture of a perfect flame coming out of a simple "T"; it is well worth a look, but why put it in the forge thread? Frosty is fond of pointing out that you need to see your burner running in a forge before judging how well it is working. I'm in the habit of judging the flame out in the open air, because I know just what to look for that way. Which way is right? Each view gives you different information. You are better off, using all the information you can get.

So, again you could ask why post on this thread instead of Burners 101? Because what you see when the burner running within a forge, and what that means when you are thinking about what burner and forge designs  are going to serve best for your purpose does belong here.  Whatever burner you are thinking about, its flame will change drastically when running in a forge. The flame will become narrower and longer; combustion will occur much faster!

Faster means hotter--when it comes to flame heat--but faster also means greater heat lost out on the exhaust opening ($$$), instead of transferring into the work and the equipment's hot face. So, when considering the flame in that photo, what would I find particularly interesting about it? I see nearly 100 percent combustion in the primary flame, but I also see the softest flame you are ever going to find producing it. Soft flames are very important for brazing work, but we are concerned with forges. So, you might say "fine, but so what?" Generally, soft flames are slower than hard flames; that's what.

So, what about ribbon burner flames; what about my own high speed tube burners? The ability of ribbon burners to produce hot flames that slowdown within a couple of inches allow them to heat up large areas for small money; a trick that will probably never be matched with anything else.  A "T" burner's soft flame is going to make it perfect for equipment being served from a straight down flame; particularly brick forges, or any other box shaped interior. Everything about the design of a high speed jet-ejector burner is designed to produce a high speed flame; that means an inevitable high speed exhaust will be produced...so, such burners will do best when their flames are set to swirl around inside miniature tube forges.

Its kind of like playing ping-pong. You begin by thinking about building a forge, which leads you wondering what will heat it, which brings you back to what kind of forge you want build, which leads you back again to just what burner will to best in it? So, which thing should you build first? You are likely to need a working burner, to help you build your forge, so it is wise to start construction with it. But the whole deal begins and ends with the forge, which is why you must begin your thinking there.

Burners and the equipment they heat work together; it should be no surprise that you can't think c-r-i-t-i-c-a-l-l-y about one, without the other.

[Frosty]

I did say it looked pretty good but the OP was in May '09, four  months before the accident. Since you started posting here I've changed my expectations when evaluating burner flames and agree that's as beautiful a flame as I've seen.

We're on the same page regarding your last post, you have to evaluate the whole tool. If you're building a burner to use as a torch then that's how you need to tune it, same if you're using it in a forge. 

I think I'll have to be more emphatic about doing the FINAL evaluation and tuning in the situation you're planning on using it.

Good post Mike.

Frosty The Lucky.

[Mikey98118]

You are right: it is a beautiful flame; something an engineer would call "elegant".

Ah, tuning; know there is a messy subject. Not messy to do. But messy to convey to the all those people who most need to understand it...and don't. I think it's a subject for video, rather than text.

[Mikey98118]

The Why of the What  in Choosing First Forges

As to heat treating: A forge is only useful to bring metal into what is called critical temperature for heat treating. For iron based alloys, such as steel, that is red heat; thereafter everything is done with water or oil based quenching, and/or tempering at much lower heat levels. However, heat treating with some alloys, like some stainless steels used in knife making, are best handled in computer controlled electronic ovens. This is because the tempering phase of the work is practically everything; also because such ovens can be used with atmospheric control. For tempering steel, the forge's burner must be used on the work out in the open air, on polished surfaces, with a very quick eye; the larger the object the more difficult that becomes.

What forge design is best depends on how large the pieces are that you want to work, and how fast you want to process them; without heavy equipment like a hydraulic hammer, you won't even want to move  parts very fast; its hard work, the faster the harder. Also, the faster the work the faster you must think. Finally, the larger the forge the higher the heat level it will cause in your shop. 

The larger the forge the more it costs to build, and the more it costs to run. Eventually, many smiths have some use for a larger forge, but will still work with the smaller forge whenever they can, to save money and keep heat levels in the shop down. The shape of a forge seldom depends on what it is going to heat, because a brick pile forge normally does a better job of working armor, etc., than any designated shape can. So, the point of oval, rectangular, or "D" shaped forges is to process several pieces more rapidly. This is also the point of shape in mini-forges; to more quickly process small parts; not to stuff larger parts into a smaller shape.

For all these reasons, shape, not size, should be a newbie's concern when wondering what forge design to pursue. Okay, money is a natural concern with most beginners, so: A "D" will not work well for guys without some sheet metal tools; a mini-oval comes from cutting an old car muffler in half; a mini tunnel forge comes from a used Freon or helium cylinder. Neither two gallon Freon or helium cylinders are  refillable, making the Freon cylinders a disposal problem for HVAC shops, and used helium cylinders a disposal problem for party supply stores.

[Mberghorn]

Sadly I built my forge before discovering IFI but I got a good bit of info from Ron Reil's pages and other various research that I'd done. I ended up using a ceramic fiber blanket called Cerachem blanket made by a UK based company with a manufacturing plant in Pennsylvania. It comes in various weights each having a different temperature rating. Mine is rated for a working temperature of 1425C (2600F). Here's the product data sheet http://www.morganthermalceramics.com/media/3993/cerablanket_cerachem_cerachromeblanket_english.pdf I didn't know anything about rigidizing at the time so I went with the 2" thick blanket. It tends to hold it's form pretty well even for not being rigidized. I have some 1" firebricks, which I bought on line that are pretty heavy so I hope they're not the crap ones that I keep hearing about on here, as my floor and they seem to do alright so far. I'll post some pictures when I get home of my build so you guys can chop it up and tell me what all I did wrong that I might not have figured out by reading all this already. I'm all up for constructive criticism!!

[Frosty]

Cerablanket is a good product. A single layer of 2" isn't ideal but it'll work just fine and yes, it holds itself in place better than 2 layers of 1".

Have you coated it? If not you can still rigidize it. What it really needs is a hard refractory flame face if it doesn't have one.

Pics please, we LOVE pics.

Frosty The Lucky.

[Mberghorn]

7 hours ago, Frosty said:

Cerablanket is a good product. A single layer of 2" isn't ideal but it'll work just fine and yes, it holds itself in place better than 2 layers of 1".

Have you coated it? If not you can still rigidize it. What it really needs is a hard refractory flame face if it doesn't have one.

Pics please, we LOVE pics.

Frosty The Lucky.

The only part that I coated was the seam because I didn't want to inadvertently melt through the forge body. I plan on ordering some colloidal silica and rigidizing once it comes in. In the mean time I'm rebuilding my burners based on the info I got from the burners 101 page (thanks in HUGE part to you and Mike).

These are the firebricks I'm using as my floor. Currently just laid in there with one on the bottom and one on each side creating a sort of U shape. https://www.amazon.com/gp/product/B000UEYZ4S/ref=oh_aui_detailpage_o03_s01?ie=UTF8&psc=1

And this is the refractory that I have. https://www.amazon.com/MEECOS-RED-DEVIL-610-Refractory/dp/B00ACIWN9Q/ref=pd_bxgy_201_2?_encoding=UTF8&psc=1&refRID=8KBNVHBDX3R958P8F2G4

Here are the pictures I have from the initial build. I'll take some pictures of the rebuild once I get a chance.

LET THE CRITIQUEING BEGIN!!!!

[ThomasPowers]

I put the seam on the bottom and cover the seam with the hard firebrick splits I use to armour the bottom.  What do you plan to use that for? It looks quite large for many tasks and of course that means more fuel used.

[Mberghorn]

On ‎3‎/‎3‎/‎2017 at 0:00 PM, ThomasPowers said:

I put the seam on the bottom and cover the seam with the hard firebrick splits I use to armour the bottom.  What do you plan to use that for? It looks quite large for many tasks and of course that means more fuel used.

The inside diameter is only about 10" but I agree that it's much too big for what I really need. I share this one with another guy that's trying to get into smithing too and he wants to make things like battle axes and short swords. I plan on building another one out of another 30 gallon barrel but I'm going to cut out the center section of it and weld it back together then most likely use 3" of fiber blanket, one layer of 2" (I have about 10 feet of 2" blanket left) rigidized, and then one layer of 1" rigidized, with a half inch of refractory and then a quarter inch of ITC-100 or similar. (Not quite sure on that last part yet) That should give me a more efficient forge and significantly cut down on fuel use.

Mostly what I want to be making is tongs and practice pieces for now but eventually pieces to sell at shows and the occasional commission. It's a good release for me (and believe me I need that) and it would be nice to make enough selling things to cover fuel costs and such.

[ThomasPowers]

Unfortunately when forging a sword you ONLY want to heat the amount of blade you can work before it cools---usually under 6" and often just a couple.  All the extra length you heat suffers degradation through decarburization, grain growth and scaling + you are throwing away money heating all that extra space!  Pretty much the only time you need a long forge for swords is for heat treating (or if you have a powerhammer and are good with it)  It's sort of like buying a dump truck as your daily driver  because a couple of times a year you need a load of gravel.   Battle axes would probably require something like a brick pile forge as they have a difficult shape to get into a standard propane forge.

This is one of the most common errors folks wanting to forge swords make---not finding out what they need vs what they think they need.

[Charles R. Stevens]

Wapping heat treat oven tho...

gass forges are realy effecent in a rather nerro range of work, many smiths have more than one. As TP points out, a forge that will heat about 6" will do 90% of your work, after that it's about heat treating or scrowling (and the accasinaly anivil ;-)

So think more in the line of a 12" cylinder 12" deep with ports on each end. Mike's suggestion of the freon can is good as well. I shoe, so my forge is built to hold two #2 shoes, but as I accasinaly shoe heavy horses I wish the door wold close on #8 shoes. I find solid fuel to be more versitile personaly (tho you are more likely to burn up stock)

[Mberghorn]

3 hours ago, ThomasPowers said:

Unfortunately when forging a sword you ONLY want to heat the amount of blade you can work before it cools---usually under 6" and often just a couple.  All the extra length you heat suffers degradation through decarburization, grain growth and scaling + you are throwing away money heating all that extra space!  Pretty much the only time you need a long forge for swords is for heat treating (or if you have a powerhammer and are good with it)  It's sort of like buying a dump truck as your daily driver  because a couple of times a year you need a load of gravel.   Battle axes would probably require something like a brick pile forge as they have a difficult shape to get into a standard propane forge.

This is one of the most common errors folks wanting to forge swords make---not finding out what they need vs what they think they need.

Neither one of us knew anything about smithing before we started other than you get metal hot and hit it with a hammer, lol. I did some basic research before discovering this wealth of knowledge and now I am a bit more informed for the next build. As I said in my last post, I'll be using another barrel of this size for the next one but only because one I already have another one, and two because I have ten feet of 2" thick blanket to use so I don't want to make my work area too small by having 3-4" of insulation around the inside of the forge body.

I'm about to come into possession of two brake drums so I'll be building a coal forge next (once I go through the pages on coal forge construction).

Also the difficulty in getting battle axes and such to fit into a standard opening for a propane forge is why the opening on this one is so big. It measures about 4"x10" give or take

[ThomasPowers]

Research battle axes too; if you want to make them like the ones that were actually used!  There are several large staff weapons and a style of 2 handed foot jousting can openers but a lot of actual battle weapons are fairly small and *fast*.  (Heavy is slow and slow is dead on the battlefield) .  One way to differentiate wood chopping axes used in battle vs battle axes is that the purpose made fighting axes tend to be *lighter*.  Also check the weights and sizes on things like horseman hammers.

Now of course if you just want to make fantasy wall hangers---go wild!

(my general test for folks is to ask them how much a medieval battle sword should weigh?)

[Buzzkill]

It sounds like you are in the typical "it's better to have it and not need it than need it and not have it" mindset as far as forge interior goes.  Been there done that.  You already have a very large forge built, so if you are going to build another this might be the time to see how small you can go and still fit your needs.  Believe me, there is a big difference in propane consumption to keep the one you have already built at temperature compared to a disposable helium or freon canister forge.  If you're mainly interested in forging straight blades, whether knives or swords, it's a good size to work with.  A mousehole in the back lets you heat enough material to work by hand without constantly heating portions that you can't work in one session anyway.  That size gives you about 5 inches internal diameter to work with, which tends to be more than enough for straight blades.  Obviously for war axes or odd shaped blades you'll need the larger forge or other options.  One way to make a smaller forge and still allow for larger pieces is a clamshell type of design.

Anyway, good luck with whatever you choose to do.  I'm looking forward to see your creations.