Mikey98118

It is convenient to be able to braze weld mild steel parts to paint cans and coffee-cans. A Tausom JH-1 MAP & propane torch, with swiveling stainless steel flame tube, can be used to braze mild steel sheet metal, tubing, and schedule #10 to #40 pipe (with the aid of brazing flux), using 70/30 brass brazing rod which has a 70-degree melting range and the steel at red heat—not 60/40, which only has a 10-degree melting range. Brazing with 70/30 filler will prove easy, when heated by MAP gas (propylene) and will handle minor gaps , but is much more work is needed, when heating with propane. For stainless steel, a silver alloy with a minimum of 56 % silver, and black flux is needed, and no gaps larger than 0.005” can be bridged.

Yup. Nevertheless, so far, all vortex burners are linear, but not all linear burners are deserves the title vortex; yours do.

Gas valves: There are three kinds of gas valves that matter to you; needle valves, ball valves, and variable pressure regulators. Ball valves are meant to start and stop flow. In a burner system, they’re mainly used as emergency cutoff in case of fire; they are also used to divert flow from one pipe system to another. They can be used to control flow, but not in a satisfactory method. While the most dependable kind of gas valve, if they are cheaply made, expect them to leak, too. To find dependable ball valves, choose gas rated ball valves from the plumbing department of your local hardware store. Needle valves are best used to quickly fine tune flow in a gas system that already has a variable pressure regulator. A good quality valve, which is new, can be used to stop flow completely, but most needle valves sold in the propane fittings section of hardware stores, will begin to leak flow, eventually. What about air-propane cylinder mount torches; they only have a needle valve, right? Expect them to have, or develop, small leaks. To ensure acquiring high quality needle valves, purchase them from a welding supply store; they sell torch needle valves in “Y” fittings for torch leads, which last for decades without leaking. Variable pressure regulators are used to limit the amount of pressure in a burner’s gas system to a little higher than the desired range you want to use; this allows rapid fine tuning of the burner with a needle valve, while protecting the hose and pipe connections from possible damage and leaking, from constant exposure to full cylinder pressure. Yes, it is possible to use the regulator to fine tune your burner, but if you have very much hose in your burner system, every change will be delayed; they are less likely to leak than needle valves, but once again, cheap regulators are not dependable, and are likely to leak. Threaded parts seldom seal gas tight; especially when exposed to full cylinder pressures, as in the case of most cylinder-mount propane torches. The common fix is to use Teflon tape that is rated for fuel gas as a sealant, but such tape is meant for relatively low pressures encountered in household natural gas lines. So, Teflon tape is not likely to work well on lines without a pressure regulator installed. Even then, they must be turned in the right direction to avoid unraveling during installation, and the tape must be kept away from the last two pipe threads to avoid Teflon shreds from migrating into the gas line; inescapably plugging up the gas jet. A surer method is to apply gas rated gasket sealant on the threads of the male connection (kept away from the last two threads on the fitting’s end). You can also employ gas rated thread sealant (AKA Threadlocker). If you disassemble the fitting later, be sure to thoroughly wipe off excess sealant from internal threads first thing, lest some end up inside the gas orifice. Always clean the gas system before assembly: Teflon shreds are not the only junk that can enter your gas system. Burrs from cutting, grinding, sanding and threading operations must be thoroughly cleaned from burner parts, and all lines and hoses cleaned out with compressed air, to avoid debris from accumulating in the small gas orifice of a burner. Debris could have collected in the fuel hose from the gas cylinder, if you rent cylinders from an exchange system, from junk in the hose, if you leave it off for a long time. Insects and spiders are attracted to fuel hoses, because of their stench of fuel vapor. Propane can leave a buildup of tar and wax in a burner's gas orifices; especially from poor quality fuel. The wrong kind of hose will rot out over time; only use LPG or multi-fuel rated hose. Never use acetylene hose! Never use air hose! Never use water hose!

Assuming that you are referring to Gas Burners for Forges, Furnaces, & Kilns, the answer is no. The smallest burner in that book is 1/2" size; it can easily be turned down enough to be used in a coffee-can forge. But I prefer a 3/8" burner size for that job. So, you can ether settle for a workable 1/2" burner in that coffee-can forge, or listen to the picky-butt's preference for the very best possible choice... How interesting. I didn't run into finicky until I built the 1/4" size Others have built the 1/4" burner using air slots in place of rectangular openings, and they ran fine, with just that little bit of de-tuning. However, why bother to build a Mickey burner if you are going to de-tune it? Thus, I became interested in linear burners, which are much easier to build in miniature sizes, and run quite well enough in any size

Two-Brick forges; maybe not The first question to address in forge design is why; what do you plan to use it for? You can temper knife blades in them, forge small items like leaves, and forge jewelers punches in them; not much else. You can forge and temper small knife blades in them. Not only are two-brick forges small, but most people heat them with propane torches, which are only rated for 2,000 to 5,000 BTUs (British Thermal Units). A 1lb. cannister of propane only contains about 26000 BTUs. You will require one of the hotter torches, running full out, to accomplish anything; so figure on that cannister not lasting very long. Therefore, the next thing you need is an adapter hose, so that you can run that torch from a regular refillable propane canister. Morgan K26 IFB (insulating firebricks; also called soft firebricks) were the first of the new insulating firebricks on the market, as far as, but there are several different varieties now; their most common measurements are 9” long by 4 1/2” wide by 21/2” thick, although they come in various thicknesses. These soft white insulating bricks should not be confused with hard yellow or orange firebricks, which are used in fireplaces and wood stoves; they are neither soft, light, or very insulating. The new insulating firebricks are all light, highly insulating, and easily cut, ground, and drilled. Plistix 900 F (use rated for 3400 °F (1871°F) is recommended over other re-emission coatings because it provides a smooth hard finish surface, to the rough ground or gouged out internal surfaces of the two insulating firebricks, and can be purchased in small amounts, from various sources on line, at reasonable cost. Here’s the bottom line. By the time you buy the torch, the bricks, the Plistix, and the adapter hose, you could make a coffee-can forge for about the same amount of time and money. But you will end up with a lot more tool. On the other hand, if you increase the amount of bricks to build a brick pile forge no larger than that coffee-can, you will have a more durable forge for your trouble.

Brick pile forges When might a steel shell amount to silliness on a forge design? Let us discuss the why of box forges. Assuming that box forges started out as a way to accommodate straight refractory products like firebricks, ceramic fiber board, and high alumina kiln shelves, deciding on a box shape is no great stretch, right? And most of us don't want such expensive materials wrecked, so steel cladding comes quickly to mind. If you are running a busy steel shop, that makes sense. If that new forge is going to live in your studio, I would recommend just keeping gorilla types outside of locked doors; this will save wear and tear on a lot of other equipment too. Just post a sign saying "no brats allowed". Keep a whip and a chair handy; brats will not leave quietly. Which brings us to what should sensibly follow in typical box forge construction: (1) For most forge sizes: Morgan K26 bricks from Technical Ceramics for floor, walls, and ceiling, makes a sensible building material. (2) Refractory cement to glue the ceiling brick into one piece, the floor into one piece, and each wall into one piece (six sides in all). Cementing the bricks together, makes your forge more stable, but hampers its ability to change size; so run your forge long enough to decide that its size and shape is where you want it, before cementing anything together. (3) The thinnest high alumina kiln shelf you can find to cover the floor, or a small sack of Kast-O-lite 30, to cover coat flame impingement surfaces on the bricks. (4) A metal plate, or hard cement board, over the ceiling bricks is a smart bet, only if the burner or burners are positioned there, and down facing. Or, use a metal plate on one side wall if burners, are mounted high up on it (and cross facing). It takes a metal cover to provide a surface to mount burner ports on vertical surfaces, or if your forge also has a hinged door. (5) four sections of angle, and four sections of all-thread, with matching nuts and flat washers to allow the angle to keep the floor, ceiling, and four walls trapped together. (6) A floor flange, pipe nipple, and six thumb screws to make each burner port used to mount each burner on the forge top, or side. Most people find a floor flange makes a good anchor for a burner portal on brick, or refractory surfaces. (7) A good burner or burners, with valves, regulator, hose, and fuel cylinder. (8) Four extra bricks (minus whatever bricks you left out of one wall to leave an exhaust opening in the front of the forge) to make a movable brick baffle wall in front of the exhaust opening. (9) Plistix or some other finish to coat the ceiling, walls with, eventually. (10) A large square pan, nearly full of Perlite from your nearest garden center to place the forge on. Beyond these items there can be a long list of added items if you like, but it will all be add-ons This list is all you need to construct a basically hot, efficient, and safe brick-pile forge.

You are right; it was Swan. Thanks, Tim.

Most of these forges call themselves forge kits; you must provide the finishing touches, like colloidal silica rigidizer, Kast-O-line 30 flame face, and even upgrade some of their hoses and regulators. Keep these things in mind, when choosing among various offers. Look for the best forge and burner, with the least accessories, because a lot of those extra goodies will need to be replaced right away.

Choosing among commercial forges There are three exceptions to everything I am about to state about commercial forges: (1) Chili Forges, while expensive, are probably the best commercial forge available today; they are the first choice for any busy shop. (2) Diamondback single burner forges are very likely the best dollar value in commercial forges; if you want your money's worth in the mid price range, you won't do better; they are fairly economical to run, get plenty hot enough, and will still be running when you retire to the golf course. (3) An unknown English two burner box forge, which I saw demonstrated at the ABANA conference at Seattle WA back in 2006. I have never seen or heard of it since, which is a shame. I have no doubt it is alive and well over there. If anyone knows of it, please speak up. So, with the glaring exceptions out of the way, I don't think much of mid price range gas forges ($400 to $600); I find them to be generally over priced and underwhelming. Which brings us to the obvious choices for a beginner's first forge; the low priced range. Since the best choice (Mister Volcano) has withdrawn from the market, you will have to choice from whats left; some of them aren't half bad; others constitute a complete nightmare. The ATkrou 200 single burner, double door forge ($140), would be my first choice amoung what is left; they use a an upside down "U" shaped sheet-metal body; its singe burner is centrally located, leaving the flame to impinge on its far wall between its two exhaust holes; this is critical. The two burner model has the flame aimed toward the exhaust holes; avoid the two burner model. On the plus side, the burner is a competent design, and the interior of the forge is a "D" shape; this will provide more usable space for your heating parts. Various stainless steel oval forges come and go; I bought one, just to use its parts; at $139 dollars it was a good deal, even though I build burners and forges. Nelyrho offers several different low priced forges and casting furnaces, with good burners, to choose from; you can find their site on Amazon.com, and peruse some of the best low priced equipment on offer.

Imagiwho what, now? Sounds complercated, Frosty.

Good point; we all had enough of "special people" at work; it would just suck to come home for another round of the same old thing--ugh! What I liked best about being a welder, was flipping down my helmet, and saying good by to social interactions, for hours at a time.

He was pretty sick of it by the time I met him Thats quite all right Frosty. Having done my good deed for the day, I'll just slither off, back under my rock

Lots of folks are willing to build their own forge, but shy away from burner construction. "To each his own." However, while there are always lots of forges for sale, burners come and go on the market. Hybrid burners are gone. Mister Volcano burners are gone. The Burner Guru died, and his modified Mikey burners are gone. I'm not sure if Larry Zoeller of larry Zoeller Forge is still selling his "Z" burners or not. This leaves various linear burners, a hand full of tube burners, or other jet-ejector burners around, at present. Good luck to the poor novice trying to sorta good from just plain awful designs. What to do? Here's a hint; the operative word is "design." If the design permits small changes, you can probably improve the burner, should it turn out to look better than it runs; if it doesn't, then good luck; you're really gonna need it! So, what to look for in a linear burner? An opening diameter that is at least 2.5 times that of the inside of its mixing tube. A 3:1 ratio would be ideal, but don't even bother looking for one of those. The smaller the opening to mixing tube ratio the weaker the burner will run. You can fix things like an over size gas orifice in a linear burner, but if you must change the funnel entrance, you would be better off to build a burner from scratch. So, what do you look for in a tube style jet-ejector burner? Hopefully, rectangular air entrances; their actually are one or two of them on the market...presently. Most of those turkeys have enough air holes drilled in them to be reminiscent of a gum ball machine However, there is at least one burner on the market presently that just has a few holes drilled in line with each other; this means that you can use a rotary tool and cutting discs to cut out the material between for and aft holes, turning them into slots. And, presto chango! Your rattle trap burner becomes a nitro dragster Could it really be that easy? Probably not; you will most likely need to change the gas orifice out for a different size, too; I think you can manage that. Frosty "T" burners are being copied for sale by various people; most of them look like they could be tweaked to run correctly. Just ask Jerry for help with them. That's okay Jerry; no thanks needed (anything for a my good buddy)

What goes where is all about the WHY Tunnel forges are today's most common shape for home construction, because of the variety of steel containers, which can be recycled for their use; they are also the easiest shape to swirl heated internal atmospheres in; and that is a convenient way to increase hang-time for those expensively super-heated gases (by lengthening their exhaust path). Cylinders also provide strong light shells, with good heat dissipation from ambient air currents around their bottoms; this greatly eases the problem of heat transference into supporting surfaces, such as your table. However, tunnel forges do not make the best use of their interior spaces, and so they are giving way to oval and "D" shaped forges, which do a better job of it. Box shaped gas forges have been around since long before tunnel forges started being built. Since they obviously provide far more usable room than tunnel forges, why did tunnel forges ever get started? No; it wasn't just that paint cans were convenient. The gas burners that heat those forges got better (as in hotter), while their fuel cost rose considerably higher (propane versus the price of natural gas). Furthermore, back in those "early days," people were concerned about even heating, which was a concern with box shaped interiors. However, hotter burners, better insulation, and re-emission coatings have pretty well ended those problems. Placing burners high up on one side wall, allows them lots of room to finish combustion before impinging on the far wall, and keeps them well above your heating steel, most of the time. If you want to heat up a bowl or helmet, top-down facing burners are the ticket. What then; do you need two different forges? No; you need to make removable refractory plugs to to cover extra burner ports, when they aren't being used. Then you can reposition your burners at will. But isn't that a lot of added work? Not if you actually have need of them. Well, it kinda looks like we went full circle, yes? No; circumstances, and technical advances are always going to alter cases. The point is knowing why what needs to go where

It is hard to imagine some of those designs actually being patented

It makes a difference both ways. Commercial forges are made for profit, and that becomes a huge factor in their deigns. Angled burner ports are far more work to get right. More work makes less profit. All us "DIY folks" remain quite serious about performance, which usually, but not always, calls for angled burner ports. It is possible to mount burners high up on one side wall of a box forge, and get could circulation in a forge.

Surprise The more we know about any given topic the harder it is to learn something new. Chile Forge employs my high speed tube burner design (AKA "Mikey" burners). The thing is that all the Chili forges, are designed for rock and role; not for waltzing. Whether one or multiple burners, those forges only come in one burner size; and that is one-inch. Furthermore, I designed all my burners for a minimum gas input of between four and seven PSI positive gauge pressure (the larger the burner the higher the minimum pressure). While cruising the web, I stumbled across a discussion between some Chili Forge owners, who where having trouble getting their forges down to cool enough temperature for blade tempering. One of them came up with the idea of ordering the next size smaller MIG contact tip, then what came in his burner. Now, as the guy who designed this burner; that would be the last choice I would ever make! Ordinarily, the smaller the gas orifice the leaner the burner will run, and those burners are already set to produce a perfect compact neutral flame. However, circumstances alters cases, once again. It turns out that the undersized MIG tip was just the ticket to allow him to get away with turning a high speed tube burner down to one PSI gauge pressure, and tempering his blades. Who'd a thunk it ?!?

Rigidizer Common rigidizer for ceramic blanket consists of colloidal silica (AKA silicon dioxide flour; synthetic amorphous silica; hydrophilic fumed silica; silicic anhydride; pyrogenic (fumed) amorphous silica. It is colloidal (does not settle out of water), both because of its slight weight (2.3 lbs. per cubic foot), and the small size of it’s particles, in flour form (0.2 to 0.3 μm average particle size).

Aligning reducer, or “T” fittings, to mixing tubes: Most burner designs are considered easier to make with threaded plumbing parts; that can be true, or far from it; depending on the quality of those parts. Cheap imported fittings are becoming the rule as steel water pipe is marginalized by copper and plastic. Cheap pipe fittings are often made from marred castings, which don't thread properly, producing axially misaligned threading in the finish part; such parts make burners that cannot be properly tuned, and thus produce poor flames. Here are some answers to this problem: (1) Avoid buying threaded fittings from large generic hardware stores. They don't have a good selection of fittings, and tend to use cheap imported stock. Look for regular plumbing supply stores or HVAC supply stores, instead. (2) Hand screw fittings and pipes together, and inspect them before purchase; crooked fittings are easily spotted this way. Don’t stop with screwing the reducer to the smaller pipe that will be used as its mixing tube; add a larger pipe on its large opening and revolve the assembly in your hands. Whether the parts are axially true or not quickly becomes apparent. (3) If you must buy your fittings online, consider using stainless steel instead of cast iron; stainless parts are likely to be much higher quality. (4) In the end, the surest answer to a problem, is to avoid it. Every threaded pipe fitting has a much higher quality butt-weld equivalent. Pipe can be used in the next smaller size to the fitting's opening, slid into position (after a little power sanding, or grinding down, if it is oversize), and held in place with socket-head setscrews. This is a little more work than screwing together threaded fittings, but gives much better part control, and superior flow. Don’t forget to grind an internal bevel on the end of the pipe that slides into the reducer fitting.

But, doesn’t a propylene fuel cylinder cost a lot more than a propane cylinder? Yes, but if you construct your forge with the intent to switch from propane to propylene fuel, eventually, this expense is not part of your original costs. But, aren’t you forced to switch to propylene, to recover your additional construction costs? Again, the answer is no. Refractory materials within your forge where out from accumulated heat damage, over time. The better the materials used the longer they last.

A five-gallon used propane cylinder forge/furnace Most home casters use a five-gallon used propane cylinder for their casting furnace's shell (container body). I normally suggest a two-gallon cylinder as a shell for your first gas forge, but if you also want to build a casting furnace, the five-gallon propane cylinder can usually be picked up for free at most places that sell propane; this is because cylinders must be tested every ten years, to see if they can be legally refilled. There are usually old cylinders lying around, which can no longer be legally refilled. Propane dealers are happy to give away old cylinders, left behind by customers who replaced them with new cylinders. The biggest difference between tunnel forges and home casting furnaces, are whether they are positioned horizontally, or vertically. An extra four legs, which extend several inches beyond the forge shell's far (bottom) end, allows that placement; their extended legs also enable the forge to sit several inches above a sand filled pan, so that liquid metal can discharge through the bottom emergency spill hole, and into the sand, in the event of crucible failure. You also need to have the forge shell’s near (top) end; carefully cutting it off, in a flat plane (hopefully using a welded seam on the cylinder as your guide), and hinged back on, with a latch added on its other side, so that crucibles can be lowered into the furnace and picked up out of the furnace with crucible tongs. Some people include A hinged door on the exhaust opening end of their forge, for ease of refractory installation and repair; also, for the ability to heat larger parts in the forge than would otherwise be possible). You simply include about one-fourth of the wall to the door for convenient crucible use. You will also want the inside surface of the far end of that forge to be perfectly flat; I recommend using a small round kiln shelf for the purpose, instead of cast refractory; it is simply easier to get right. Instead of a smaller exhaust opening, you drill an emergency spill hole clear through this end (at least 3/4" diameter). Instead of a flat forge floor, make the wall entirely round, and slide a rectangular kiln shelf unto it for forge use; leave it out for furnace use. Use two 1/2" burners (placed a one-third distance between both ends), instead of a single 3/4” burner. You shut down the top burner for casting, and only use it for forge work. You can also place a temporary internal baffle wall on the kiln shelf floor, and shut down the far burner, to save fuel when forging small parts. Should you take the second burner out of the forge when it's not running? So long as a down-facing burner's air openings are kept closed, leaving it in place should be okay. But double check the fuel hose to that burner, to insure it isn't heating up, due to the lack of cold incoming propane vapor to cool it down; if its hose is heating up too much to touch, it is safer to remove that burner and hose, to keep it from overheating. As to the burner that is kept shut down; so long as its air openings are kept closed by the sliding choke, there should not be any overheating from chimney effect. The exception to this is a burner with a fan attached. Any fan driven burner, must not be left in place, when shut down. However, it is a simple choice to make the burner in these forges up-facing, since the wall is entirely round, and the floor is slid in and out; this avoids many problems. First class refractory and insulation choices are often considered too expensive to be used in larger forges; this is a mistake. Propylene fuel costs about one-third more than propane, if used from refillable cylinders; it also gets about one-third hotter, which means that the burners can be cut back that much, for the same heat level in your forge; or smaller burners can be used, which is even better. Either way, the exchange rate of internal atmospheres will be slowed; this reduces fuel consumption for work heated, since most of the heat loss in forges and casting furnaces is straight out the exhaust port. Employing propylene calls for more expensive materials in the forge and in any flame retention nozzle, to withstand increased flame temperatures. Thus, cheaper building materials costs far more than they save!

Well put, jcornel

Your sleeve is a primary choke; it controls air flow into the burner. A secondary choke slides up and down the burner's forward end, controlling induction of secondary air (by the flame) into the forge, through the burner's portal, which that burner is mounted through.

Yes, and furthermore, a lack of precision input leads to a lack of precision output In larger equipment; especially if burning natural gas; this is not necessarily a big deal. But the smaller the forge the more inconvenient that becomes.

Burner Ports: Once you build a burner, you need to install it in your forge or furnace, which brings us to burner ports. Some people just drill a hole in the steel shell and a matching hole through the refractory layers, but this doesn't provide support for the burner or any way to fine-tune its aim. Most of us attach a short section of larger diameter pipe or heavy wall tube to the outside of the shell, and use six thumb screws, in two rows of three screws each, to trap and aim the burner. Note that: (A) Pipe or tubing can be arc or braze welded over gaps in sloppy fits, but silver brazing requires close fitting parts. (B) Larry Zoeller uses a 1-1/2" by 4" long schedule #40 pipe nipple with two 1-1/2" conduit locking rings, and two 2" by 1-1/2" rigid conduit reducing washers to mechanically affix a burner portal (for his 3/4” burners) into a hole in the forge shell. (C) Jerry Frost came up with an excellent method of mounting his burners directly onto brick or refractory surfaces; he threads a pipe nipple into a floor plate; a simple and effective method that can be employed on any flat horizontal surface. Control of secondary air: Now let's discuss the induction of secondary air and unwanted cooling of the equipment. Even single combustion envelope burners can benefit from external cooling air if the burners penetrate extra thick insulating layers (more than 2"), or the burners are very small 3/8" or less, because internal cooling from the cold incoming fuel gas could be overcome during long heating cycles, under these conditions. Most burners have at least secondary flame envelopes, so some builders deliberately leave their burner ports unsealed, because secondary air induction (powered by the flame) is needed for complete combustion of such flames. Unfortunately, this usually leads to an overabundance of a good thing, because the flame becomes an even more powerful induction "motor" than a burner's gas stream makes. It takes energy to heat air, so extra secondary air becomes a drag on performance within the equipment; leading to as much as 20% heat reduction. Fortunately, you do not have an if/or choice to make. It is just as easy to control incoming air through the burner port as incoming air through the burner, by the use of a sliding choke mounted on the burner’s mixing tube. Simply employ a washer brazed to a short thick tube, drilled and threaded for a thumb screw, on the burner. Once the burner is installed, it can be slid up against the portal tube's end to seal the port against heating from chimney effects after shutdown, and slid closer or farther from the portal tube for secondary air control during operation. Is this more work? Obviously, but you should expend the additional effort; especially because it is an add-on project, which need not delay getting your forge up and running. Existing tin cans and paint cans make cheap and easy equipment shells, with built in bottoms, which makes them irresistible for most first-time builders of portable forges and furnaces. When someone mentions making a shell from light sheet metal and pop riveting it together for more convenient diameters, most of us just shrug off the suggestion. But recently I stumbled across double wall chimney inserts that are filled with...you guessed it; ceramic fiber. Naturally they are too expensive to be tempting, but they got me to thinking... Two different diameters of sheet metal forms, pop riveted together, could be filled with Perlite that is glued into a monolithic shape, with plain old water glass (sodium silicate), making a highly insulating and rigid furnace shell for a minor monetary outlay. And since such cylinders can be made into larger diameters than the usual shell sources, they could also contain an extra layer of insulation and still have plenty of room left inside the shell for hot-face and insulation layers. Oval forges: Of course, the builder does not need to make a tubular shape; this kind of shell would also lend itself nicely to oval shaped forges...light sheet metal can easily be cut to any desired shape for front and rear faces. By making the outline and then a larger outline 1/2" outside and parallel to it. Room is left between inner and outer shell, to cut out tab shapes with a drill and rotary tool; these can then be bent 90 degrees. Holes can be placed through the tabs and the outer shell wall beneath, and the tabs can be pop riveted in place, strengthening the shell into quite a rigid form to add the insulation into; afterward, this form is little heavier than a simple tin can, but far tougher. Burner ports can be attached to the finished form by employing a hole saw, to drill through both walls at the desired angle, forming four drilled tabs on one end of the tube, shoving the tube through the holes from inside the shell, drilling matching holes through the inner shell, and employing pop rivets to hold the tube in place. Or, the tube can be silver brazed to the outer shell. With the tubes penetrating two separated sheet metal walls, the burners will also be held rigidly in position. Forge size: It is a natural desire to go for the largest forge you envision yourself ever needing; and that is nearly always the wrong move. There is no such thing as a forge that is too small; if you outgrow a smaller forge, you will still find yourself using it whenever possible, to save time, money, and heat build-up in your shop. On the other hand, an oversize forge usually ends up collecting dust in a corner--to save time, money, and heat build-up. Building costs of forge construction are directly proportional to size. What’s worse is that you may end up choosing second rate refractory materials, and cheap burners, to save on construction costs in larger forges; this can end up tripling the expense of running your forge. The larger the forge interior the greater the heat loss through the walls, ceiling, and floor. The greater the heat loss the more fuel that must be consumed to keep the interior super-heated, which leads to increased heat lost through the exhaust opening.