Forges 101

[Frosty]

Who's clamshell forges are you talking about Mike? I wrote them off on first sight as one of those good ideas that were unworkable. You can't open a HOT clamshell forge without lighting yourself on fire. Oh okay it takes a couple seconds to flash over just not as long  as it takes to remove something from the forge.

We banged ideas around to make them workable when they started showing up. Back in theforge.list days that is. I know a number of guys went ahead and used them but not many. 

Seriously, even a small cylindrical forge say  an ID of 10" x 10" when split down the center will present a surface area over 150sq/in. That is about 150 sq/in of 2,400f+ radiating directly at YOU. My forge was hitting around 2,600f and you has to keep the opening aimed away from your working position or it'd roast you like a marshmallow anywhere within 8'. That opening was IIRC 5" sq. 

I believe some of the more stubborn folk continued to use clamshells for a few years, maybe for specialty things, maybe with a way of handling work without getting close to it when open.  I haven't heard of anybody using one in year, ideas for making one sure but not actually using one more than once.

Frosty The Lucky. 

[Mikey98118]

Actually, I included a clam-shell forge in the book; it was an accessory to go along with the hot-work bench, which had a built in burner, facing up through the brick. This arrangement allowed me to store the clam-shell top below the bench, and lay down a temporary brick pile forge, in any pattern desired. I was planing on doing hot glass work on that bench too. 

I did not find a problem with heat, when the top half was opened, because the top shell was rigged to open and close quick and easy with a counter weight. The problem is that very few people will find use for them. I built it to be able to work on scroll panels, and metal baskets. However, health problems shut down my plans to get back into the ornamental iron business.

[Frosty]

Not the run of the mill clam shell forge and I don't know enough about glory hole to have a valid opinion. My question though is, How much liner was radiating directly at you with it open? Even briefly the IR cooks you unless you're wearing thermal PPE.

My 4 burner variable geometry forge was made for doing large work but very little of the liner radiates at my even when open. With the internal partitions removed the floor is 18"x18" by whatever height I set it with the jack.

It still roasts you like a kabob.

Frosty The Lucky.

[Mikey98118]

I think it boils down to expectations, for one thing. What do we think is excessive discomfort, compared to creating what is desired. Another factor is how the top shell  (lid) moves; if it is quick and certain, and if you arrange to limit the height before you heat up the forge, the actual heat exposure is greatly reduced. But, as I pointed out before, the real limit to these forges, is what they are desired for; that would be nothing whatsoever for most smiths.

However, when slumping  hot glass into wrought iron baskets, etc., run of the mill forges just won't do the job.

I wrote that book to help show young artists how to get something worthwhile from their college degrees. An artist's reach extends no farther than his tools.

By the way, I misremembered something about the clam-shell forge attachment. I made it just to late to include it in the book. The publisher wanted me to wrap things up, after waiting two years for me to get done 

That's okay, If I couldn't regret the loss, there would always be something else to obsess about. So, I forgive me...mostly

[Mikey98118]

Frosty,

I was thinking about your comment maybe adding a wave pattern on the floor of your next forge. If the pattern  was something like an inverted coil all the way around a forge interior, I wonder if it would encourage increased hang time for exhaust gases?

[Frosty]

I hadn't thought about hang time, it could I suppose. I was thinking for my next prototype forge, a round chamber with a dome roof and two NARBs with outlets angled longitudinally, mounted offset parallel and tilted slightly toward the center. The walls in two sections that can be moved around the circumference to open, close or position the work's orientation to the burner flame curtains.

All the above isn't so much to put the work in the fire but to position it over the hotter sections of the corrugated floor. Being offset and the opening positioned right there would be a narrow hot zone one could heat small sections of a piece, say a rivet without heating the entire piece. 

Angled differently either by moving the walls (not my preference) or rotating the dome to place a piece parallel with the NARBS there would be a hottest zone between the impingement lines, sort of a tunnel or channel for heating long sections. 

Some "features" are almost mutually exclusive, largely the above benefits of parallel NARBS and tailored hot zones and the dome lid. My thoughts for the dome was to act as an IR lens directing the bulk of the IR towards the center of the round floor and perhaps the most likely benefit provide a smooth round surface to not inhibit the flame flow.

The NARB outlets being angled in opposite directions to induce the flame to spin around the floor like a record player

The above is or was the basic idea and I've found so many holes in it on the drawing board I haven't even laid out a pattern for the corrugated floor or made the NARBs. These are mostly construction details and I'm pretty good at this kind of thing. Or used to be. 

I just don't know how much I'd use it, I don't spend a lot of time at the anvil anymore. 

Anyway, that's where my thinking for a new prototype is hovering. My Current NARB forge has a long list of "flaws" being a prototype and the too large shop forge still has the flaws it had since birth. I'm also seeing some really good different burners online I'm awfully tempted to experiment with.

Frosty The lucky.

[Mikey98118]

The corrugated floor is a useful idea, that you have been thinking about for a years, yes?

IR lenses is a new twist, which I will now be thinking about for years. Previously, I have considered the whole interior of the forge as incandescent, so that the energy was reasonably well trapped, and available to be soaked into the work pieces. But this is because I haven't bothered working with hot-spots in the past.

One pal of mine built a tunnel forge, with a single top-dead-center down-facing 1/2" Miking burner, which he used to heat 1/4" square bar to red hot, for wrought iron presents. Bud was very into focusing the flame directly on the work pieces, to get the most work done for the least fuel expended.

I have always intended to use a similar design to find out just how small a forge could be used to build chasing tools for jewelers. Perhaps a bean can forge, with twin 1/8" burners?

"Miking burner"? Time for a big cuppa!

[Frosty]

IR radiates like all "light" frequencies of EMR. Radiation is similar to reflection and I hope a dome will work to concentrate the energy where I want it. To a degree at least. Cylindrical forges have a hot zone running down the center of the chamber rather than the floor. 

 I could certainly be wrong about that being "focused". The domed forge should if not answer that for me, give me clues. 

I've tried corrugating Kastolite a couple times and wasn't impressed with the results, my methods are lacking. So far.

Frosty The Lucky.

 

 

[Mikey98118]

I think you're right about focusing. The only question is whether it turns out as a major or minor factor is use.

Shaping the inside; the devel is in the details. Employing something like a form of sticks and paper mache, with a sealed surface?

[Frosty]

I'm using a plastic pool ball I'll wax heavily. It will fit in a hole I cut in an old highway sign to form the bottom of the dome. I may start by plastering the ball with Kastolite 30 and then covering it with Kaowool and then given a final coat on the outside of something hard and or rigid for support.

It'll rest on a circular forge wall which  will sit on a floor. None of it bonded together there will just be tracks or maybe ridges to keep it in position. One thing I'd like to be able to do is lift ad turn the dome to realign the flame curtains and maybe move the wall halves to open or close doorways. 

I have yet to model the idea so a lot is just blue sky thinking.

Frosty The Lucky.

[Kenny O]

On 5/7/2023 at 5:08 PM, Frosty said:

Kenny: I the Iforge store carries Plistex, the link is at the top of the page under gas forge supplies I think. They were out for a while but I'm sure Glenn has restocked.

Frosty The Lucky.

Thank you!

 

On 5/7/2023 at 6:23 PM, Irondragon ForgeClay Works said:

If you do a search using your favorite search engine like this,

  Mr Volcano site:iforgeiron.com    It will bring up about 71 results for your viewing.

I can't control the wind, all I can do is adjust my sails. ~ Semper Paratus

 

Thank you!

[Mikey98118]

                The ends and outs of quick-connect fittings

Also called "quick-disconnects"; these fittings were originally designed for use on oxy/fuel torch hoses ( that kind have revers-flow valves built in, and sold as a pair; fuel, and oxygen couplings). Such pairs cost between fifty and sixty dollars.

However, quick-connect low pressure propane fittings are sold for as little as $12. And why should you care? It isn't only hand torches that get swapped out. If you have been using a gas forge very long, you are likely to have two or more of different sizes and shapes. The easier they are to change over, the more use you will get from them.

GASPRO Low Pressure Propane Quick Connect Fittings Kit ($12 at Amazon.com) includes a built-in shutoff valve. You need to have a 0-30 PSI pressure regulator on the hose that feeds this connector. Also, don’t place a quick connect next to a hand torch, or the constant  swiveling of the hose will wear away the its seal, causing it to leak (leave a few feet of hose between it and any hand torch).

KIBOW Propane Quick Connect Fitting-Full Flow Male Plugs ($8 at Amazon.com). A quick-connect fitting needs more than one male fitting (plug) to be of any real use.

[Mikey98118]

 

Employing a propane adapter hose

 

Propane extension hoses (AKA adapter hoses) are marketed to allow campers to run portable gas stoves on refillable propane cylinders, instead of the 16 oz. none-refillable canisters that backpackers prefer; some of them also allow you to do the same with canister mount torch-heads.

    These hoses all have a QCC type connector fitting at one end (which screws into your canister-mount burner). The hose’s other end may have a QCC connector fitting meant to mount on a canister, or a POL fitting for refillable cylinders. Even the hoses with QCC connectors on both ends are helpful, as they allow the burner to operate as a hand torch more easily, and to separate the fuel source from hot equipment by a few feet.  

    There are hoses that include variable pressure regulators, and hoses of varying lengths. Hoses with stainless steel armor braiding are the best choice, whatever their length, for service near hot equipment (or in busy metal working shops). I don’t like standard heavy wall propane appliance hoses; they are stiff and overpriced. However, adapter hoses are not stiff, and have reasonable prices.  Braided armor stainless steel propane hoses, are also available with 3/8” flare nut connector ends, which can be matched up to propane flare fittings available at some large hardware and appliance stores.

[Mikey98118]

Propane versus propylene

The only fuels you should be concerned with in a portable gas forge are propane (or LPG mixtures in Europe) and propylene; both are LPG fuels (liquid petroleum gas); both are heavier than air.

    Adiabatic temperatures are the mathematically derived greatest possible combustion temperature of a given fuel; that of propane and propylene burning in air are little different. The actual flame temperatures of air-propylene flames are about one-third hotter than that of propane. Why? Because in the real world, how hot a flame burns depends on how well the burner’s design can combust the fuel; most hydrocarbon fuels will burn at about the same heat in a jet engine; the richer hydrocarbons will simply require less fuel flow to do the job. How hot fuels get in an air-fuel burner, or oxy-fuel torch, varies widely.

    The so-called MAP gas, sold in 16 oz. yellow canisters at hardware stores is propylene; “MAP” is an advertising ploy, that was probably meant to be confused with MAPP gas, which hasn’t been produced since 2008. MAPP only claimed to produce fifty degrees hotter flames than propylene anyway.

    Propylene costs about twice the price of propane in 16 oz. canisters, but only about one-third more than propane in refillable cylinders down at your local welding supplies store. Since it provides about one-third more heat, this fuel might seem to produce no major advantage in heating equipment. But, no matter how cleverly you design a forge or furnace to reduce exhaust speed, its lower limit depends on how fast fuel must be combusted to attain desired internal temperatures. So, propane’s lower flame temperature, sets an unexpected limit on efficiency. Of course, when you use your burner as a hand torch, propane cannot compete with propylene.

    Propylene runs at higher cylinder pressures than propane at any given ambient temperature; therefore, propylene cylinders have thicker walls; outside of these differences, you’ll find that safety regulations are similar for both fuels. Propylene's much higher flame temperature will call for refractory flame retention nozzles when burners are placed in equipment interiors; kilns, furnace, and forge interiors need use-ratings to be upgraded over what you would normally choose for a refractory hot-face that’s only heated with propane; or you can reduce burners to the next smaller size, to what is recommend with propane fuel. Also, make sure to position your burners so that they have the maximum possible distance before flame impingement on the refractory hot- face.

[gewoon ik]

You can also use buthane (if still available) bit cheaper but it is useless below 5°C ambiant (it freezes), so with heavy draw of the tank, you need 10°C ambiant temperature or mixtures of both (but more expensive option vs propane for no extra advantage)

[Mikey98118]

At present, both propane and butane are readily available in Asian metropolitan areas. But while butane was available in the past, LPG (a combination of propane and butane, with traces of methane) is what is readily available in Europe now. In the U.S.A., propane is readily available, but butane is not.

Except in 16 oz. cartridges

[Mikey98118]

 

Why and why not to choose a coffee-can forge

 

There seems to be some confused ideas about coffee-can forges being a super cheap way to get into blacksmithing. What they actually are is an economical way to forge small parts, after the forge is built; their real economy comes in minor fuel use. They are also highly portable and compact tools, for those with limited space. The only savings encountered in their construction will be in the economies of scale. You can find ceramic wool blanket offered in squares that are large enough to work in a C-C forge, so you spend less money for it. But you end up paying a lot more per square foot. Castable refractory can be purchased in five-pound bags, but at double its usual price; these are the smart choices.

    Mixtures of Perlite and water glass (sodium silicate) are going to melt in short order, if you heat the forge up full blast. Perlite and furnace cement are going to break down more slowly, but they still cannot hold up to flame impingement. You would need Perlite and castable refractory to do the job, and then you have just spent enough almost enough money to buy that square of ceramic wool blanket and a five lb. bag of castable refractory. The infamous plaster and sand 'refractory formula' is such a major heat sink that you will end up throwing your forge in the garbage before this so-called refractory has a chance to crack apart!

    The second cheap and easy idea about C-C forges is that you can simply run them with propane canister-mount torches. There are only a few higher priced propane torches that have stainless steel flame nozzles, and those nozzles are so thin that they quickly oxidize away inside of a forge. Most of these torches have brass nozzles that will melt inside a forge. So, the torch cannot be placed in a sealed burner port. Instead, it can only be placed in an oversized hole, if it is weak enough, or aimed toward the hole from outside of it, if it is one of the hotter models. Either way you go, the torch is destroyed, or the forge is under powered; the answer for this is to replace propane with propylene fuel, at twic the price!

    So, you need a real burner. But, if you're going to the trouble to build a burner, you want it placed in a forge that is worth it, right? Now you have another problem, because a 3/8" burner is the largest size you can use in a C-C forge, but by the time you have constructed it, you will not want to waste it in a cheaply built "temperary" forge. There are plenty of burners you can build in the 1/2" size, if you are willing to put them in a typical mini-forge (built from a two-gallon non-reusable Freon or helium cylinder).

    Coffee-can forges have their place, but trying to use them as a cheap and easy way to heat some steel isn’t very bright; that's what charcoal if for.

    3 lb. coffee-cans (used for years in coffee-can forges and casting furnaces) are about equal in size to 1 gallon paint cans, or #10 tin cans, or four-quart kitchen pans.

[Mikey98118]

                                             The two-brick forge

Box shaped forges are the logical choice, when you use insulating firebricks, or ceramic board insulation in a forge. If you employ hard ceramic board as the flame face material, with ceramic fiber blanket for secondary insulation, then a sheet metal shell is needed. If you choose insulating firebricks, nothing more than four threaded rods and four pieces of steel angle stock are needed, to hold the larger “brick pile” forges together, or furnace cement, Plistix 900, etc. to glue the bricks together for a mini-forge.

    The two-brick forge is merely chiseled out of soft insulating firebricks; since the bricks are wider than they are tall, carving out two halves of a cylindrical shape is ill conceived; it is just as easy to carve two halves of an oval into the bricks; creating a larger chamber to work in. It is also best to leave one end of the hollowed-out area closed. Drill the hole for your burner two-thirds of the way toward the forge’s closed end, and slanting upward a little bit, to encourage the hot gases to swirl its way toward the forge’s open end. Seal the brick’s internal surfaces with Plistix 900, so that they will last well, and the forge will get hotter.

 

   

 

Note: The burner hole should be about 1/16” larger diameter than the burner’s flame retention nozzle, to keep its expansion from cracking the brick, during heating cycles, and to provide a little secondary air, which most burners need for complete combustion in the forge.

[Mikey98118]

Note: Dual-fuel torch-heads (emplyed with propane and propylene gases) usually have thin-walled stainless steel flame retention nozzles, which can be slid into thicker walled stainless steel tube, to protect them from high heat oxidation losses.

[Mikey98118]

The Two-gallon mini-forge

Mini-forges have been built for years from empty non-refillable helium tanks (sold for inflating party balloons), or empty non-refillable refrigerant gas cylinders used by HVAC companies; so far as I know, Ron Reil first posted one of them to the Net. By law, empty nonrefillable cylinders must be properly disposed of (which costs money), so they are not hard to talk businesses out of, once you explain what you want to do with them. This size forge can be run from one ½” burner, or two 3/8” burners.

    A more recent knife-maker’s variant on two-gallon tubular forges, are mini-oval forges; these were first made from truck mufflers that were cut in half. But stainless steel oval trash cans can be made to serve with a lot less effort, with superior results; they should be run from two 3/8” or three ¼” burners, placed high on one side, and aimed slightly up and toward the forge’s far side.

2.09-gallon stainless-steel oval trash can; 10.9” wide, by 9” long, by 6.4” high. Use three ¼” or two 3/8” burners; ($23.49 through Amazon.com).

[Mikey98118]

Five-gallon forges

Five-gallon propane cylinders were used for most of the early home-made gas forges and casting furnaces; they are still the most popular container size for “tube” and “D” shaped forges; these forges are at their most efficient, when run from two 1/2” size burners, placed low on the wall a little higher than the forge floor; aimed up and inward, so that the flame has the longest possible path to combust all oxygen in incoming air, before it can impinge on heating parts. With the burners placed at one-third and two-thirds of the distance to the rear of the forge, the far burner can be shut down, and a movable refractory baffle, placed midway between the burners, portioning off one-half of the forge, to save fuel, when heating small parts. This strategy works best on forges with a hinged and latched end door.

 

20-quart stainless steel canning pots are available on eBay for $26; this is equal to a five-gallon propane cylinder in area, and is a slightly more convenient shape. Five-gallon steel paint cans have also been employed.

Five-gallons is the favorite size container for casting furnaces, and the main difference between a tube forge and a casting furnace is that the forge is positioned horizontally, and the furnace is vertical. With a little added work on its legs, and the addition of a rear hole to let liquid metal escape into a metal sand box (in case of crucible failure), a forge, with a hinged and latched door, can be made to do both tasks.

[Mikey98118]

Air Chokes are a burner’s secondary control

For several years there were two very good reasons for adding chokes on burners; the first being to prevent chimney effects from overheating burners after shutdown, and the second was to vary flame characteristics. As gas burners have grown more intense, using chokes to alter flame characteristics has diminished; the technique still works, but is less appealing than it was in the past.

    Burner chokes greatly diminish chimney effects from traveling up through the burner after shutdown, but might require a secondary control mechanism (such as a moving washer on the burner's mixing tube), to stop it from overheating from air rising between the burner and its portal; this is especially true of burners with electrical fans. This washer can also serve to control excess secondary air induction, created by the flame, from lowering forge temperatures, while the burner is running.

Caution: Never trust an external washer to stop flames from backing up from the forge interior, and overheating the burner; this is the equivalent of using a bandage, when a wound needs stitches. The flame is pushing into the burner portal because of back pressure in the forge. You need to address the problem BEFORE YOU BURN DOWN YOUR SHOP! You may simply need to enlarge the exhaust opening in your forge, or you may have too large, and/or too many, or even too weak burners, mounted in your forge.

[Mikey98118]

Mounting burner ports: Typically, a burner port (entrance) consists of a short steel tube or pipe with about 1/4” larger inside diameter than the burner’s flame retention nozzle’s outside diameter. This allows enough space to aim the burner somewhat within the portal.

    The burner is held in position and aimed with two rows of thumbscrews; each row has three equidistant screws. One of the advantages of these screws is that they can hold a pipe or tube in place within the portal, and resting exactly where the flame is intended to impinge, while the portal opening is being ground into an oblong shape (to allow the tube to be aimed at a desired angle). This method ends up with a very close fit between tube and shell opening, to promote easy silver brazing of the port’s tube to the equipment shell. You are building a burner, so why not employ it to help you construct its forge?

    Alternatively, you can drill and mount a burner port in the shell with three bent flat bars and some pop rivets, or self-drilling screws. Bracketing parts together can end up looking tacky if you do not manage to keep the shell opening tolerances close. Employing screwed brackets can be a be a minor pain, if the burner’s port tube is positioned at an angle.

    Welding equipment parts, such as burner ports unto a steel shell, takes a wire feed machine and a learning curve. Some people are reworded with distortion in the shell, because of welding contraction; it only takes a little time to learn to run a wire feed welder, and somewhat more to bridge gaps with one; but it takes a lot more time to learn where and how much to weld without creating distortion. Neither brazing, or silver brazing makes that problem.

    Hard brazing requires an oxy/fuel torch, or an air/fuel torch, propylene fuel, and a lot of skill, Silver brazing can be done with an air/fuel torch, propane, and close attention to setup, but most silver brazing alloys won’t bridge gaps very easily. However, some silver soldering alloys do bridge gaps.

    Silver brazing by hand torch benefits from a lower temperature filler with broad melting range such as Ufhauser silver braze filler A-54N (54% silver/ ) that has a broad elastic range (250 °F), and bridges minor gaps; it can be considered a capping alloy, but if heated too slowly it can suffer from liquation (where the alloy separates into solid and liquid zones); it will melt between 1325 °F (dark red) and 1575 °F (bright red). The high temperature portion will melt only above the normal brazing temperature afterward. For this reason, alloy A-54N should be heated rapidly through its melting range. If you are joining a thin shell from a tin can to a thicker tube, keep the flame mostly on the tube.

    This filler alloy has a good color match to steel. Reasonable care with a sanding drum or grinding stone in a die grinder or electric rotary tool, will easily produce a sufficiently close-fit in the joint between a burner portal tube and the forge shell opening. If you’re silver brazing on stainless steel, burn polypropylene fuel gas (if you employ an air/fuel torch), and a high temperature black flux.

     Car mufflers are zinc coated, and silver brazing parts to this kind of forge shell will ensure lots of damage to the plating. Stay Brite silver solder may be employed afterward, if you don’t want to paint the forge shell. Most zinc-based soldering alloys are zinc-tin-lead (avoid these), zinc-tin-copper (excellent), or zinc-cadmium (use fume rated respirator with these and follow all safety guidelines to the letter).

Note: The main ingredient in zinc flux is zinc chloride (follow safety guidelines on container); it is the only ingredient in many of them; it tends to “tin” the surface of steel, rather than just cleaning it. If steel is freshly cleaned and power buffed with stainless steel wire wheels, it can be zinc soldered without flux, but why do things the hard way? Zinc’s melting point is 787 °F; comfortably below its boiling point (1665 °F). Zinc fumes are easily seen and smelled; avoid them. Unlike lead fumes, it takes a heavier dose of zinc vapors to cause fume fever. Unlike lead, the body can tolerate a little zinc, but keep your dose tiny; none is best. No metal fumes are good for your lungs.

Caution: Metals give off toxic fumes upon reaching their boiling points. Using zinc coated sheet metal or parts (such as car mufflers) is okay if you're careful about doing it. The boiling temperature of zinc (the point at which it makes fumes) is

1665 °F (bright red heat). Your forge shell should not get higher than one-fourth that temperature.

    But you do need to be careful to keep the shell well away from the edge of the exhaust openings, by not making the openings in ceramic fiber, kiln shelf, or cast refractory even with, or even near the shell. Zinc coated flame retention nozzles or mixing tubes are out. There is no reason at all to avoid zinc coated reducer fittings on a burner’s air openings. In other words, keep zinc away from part surfaces that may become incandescent (above 1200 °F or 649 °C).

Note: Preheat temperatures should be kept down to 600 °F (315 °C on zinc coated surfaces, such as car mufflers, to avoid damage to the existing coating on their surfaces, and to keep scale formation down on the steel; “tinning” the bare steel with a zinc chloride-based flux will help with this. Remove all residual flux with hot water and a clean rag after soldering.

    Larry Zoeller (of Larry Zoeller Forge) is credited for first mounting schedule #40 pipe to a forge shell with conduit locking rings; he calls it a “burner holder assembly.” If you’re looking for fast and easy, he sells them for $25 and shipping from his website. Their main limitation is that they can only be positioned at right angles.

    The burner port’s tube should be completely external to the forge shell; it should not extend inside the forge further than is needed to secure a locking ring.

    A washer should be provided to slide up and down the burner’s mixing tube above the portal, so that it can limit how much secondary air the burner flame can induce through the gap between the burner’s mixing tube and the portal wall. A nut can be silver brazed onto the washer, so that a thumbscrew can keep it positioned at the right distance away from the portal edge; limiting secondary air into the forge to only what is needed for complete combustion, without lowering internal temperatures needlessly. To consider air introduced from the burner opening as no different than air from other openings is a sad mistake, since those other openings don’t have flames inducing air into the equipment.

[Mikey98118]

Carbon fiber can withstand 3632 °F (2000 °C) in the absence of oxygen. So, carbon fiber could be a great way to strengthen refractory bodies, so long as both their inside and outside surfaces are carefully sealed.

[Mikey98118]

                                        Further details on C-c forges

The main difference between a tube forge and a casting furnace is that the forge is positioned horizontally, and the furnace is vertical. With a little added work on its legs, and the addition of an emergency drain hole at the bottom to let liquid metal escape into a metal sand box (in case of crucible failure), a forge, with a locking hinged door, can be made to do both tasks well enough.

    One of the hard facts of equipment design is that there is no free lunch. Everything is a tradeoff. Being able to cast and forge in one piece of equipment must be paid for with some limitations on what can be done with the door and the floor, the larger the forge, the more serious these limitations become, but in a coffee-can forge/furnace the limitations are minor, because its capacity to heat work pieces for forging was minor to begin with.