Mikey98118

No; fumed silica is what we use, in water, to make rigidizer (to spritz onto ceramic wool insulation). However fumed silica is also used as part of ceramic and refractory mixtures, because it melts-the first time, and only then-at very low temperatures. Silica spheres where originally used to create voids in concrete bridge parts, and is now also used in hard refractories, to lighten, insulate, and make it resistant to cracking. These spheres are very thin, so when they melt into the refractory (during firing), they do not increase its silica content noticeably (that would lower its insulating abilities, and lower its maximum temperature rating), but they do a fine job of leaving behind loads of voids. Did this cover your questions?

Good afternoon, Swedefiddle. To begin with, I don't disagree with a single thing you said. We are coming from two different concerns. I am only thinking about drilling pipes tubes for socket set screws, and should have preference my statement with that limitation. Also, the discussion of how to use a rotary tool, to do the job of a hand drill, is only for the sake of people who shy away from buying two different power tools, to build something they feel tentative about, already. In other words, it is newbie bait I only hope that more people will totally disagree with me, and tell us about their way of doing this work. And while I do not drill gas orifices, I will still be going back over your methods, to memorize them. There is no such thing as useless knowledge; only stuff we don't want to use, today. However...first, a big cup of java

Drilling in steel with a rotary tool This takes more delicate work than a hand drill requires. The chucks on rotary tools have a maximum of 1/8” capacity. Furthermore, these tools spin far too fast for even a 1/8” drill bit to last very long, when drilling in steel. By turning their speed down to the bottom of the tool’s range, a 1/16” M35 drill bit will work to create pilot a few holes in tubing or pipe, which can be increased to 1/8” with a tungsten carbide rotary file, and then finished with a diamond coated rotary file (both of these rotary tool accessories are sold in kits for as little as $10). Hand drilling holes with rotary tools for 8-32 thread taps (which are used on small flame retention nozzle holes for socket set screws) can be done if you are careful; the taps call for a #29 numbered drill bit (9/64”); that is 0.136”; this is 0.011” larger diameter than the 1/8” shank limits of rotary tool chucks, so you need to enlarge the holes left by a 1/8” rotary file. Drill, and then file or grind, at one-half speed in your rotary tool. Enlarge the hole a little bit with a diamond coated rotary burr. You are removing only 0.006” all the way around the hole’s periphery. So, you want a tool that works smoothly, and just slow enough to keep control of the process. Swing the diamond coated burr lightly around the hole’s edge, and check to see if a taper tap will thread in the hole easily. If not repeat enlarging and checking. Be sure to keep track of how many passes produce the desired result. It is wise to perfect your technique on scrap steel, before enlarging holes in your flame retention nozzle parts. There are tungsten carbide rotary files with heads up to 1/4" diameter, so at need, this process can be used for larger screw holes in sheet metal parts.

Why would that be? Inbuilt speed control circuits on most power tools are tiny; they rapidly heat up, when engaged. The slower you run your tool the faster they heat up. Before you know it, your tool "makes magic smoke" and dies. Then, you must either throw the tool away, or replace that dead circuit with a length of wire, because very few foreign made tools have replacement parts available. Thereafter, you will need to mount a fan speed controller to the tool's power cord, to vary its speed; these have sturdy power circuits, which are designed to take the load. BTW, fan controllers work smoothly through their entire speed ranges; most miniature control circuits, built into power tools, do not.

Electric motors, which are only rated for intermittent use are designed to be run for short periods. Of course, the higher a motor’s amperage, the hotter it gets. Power equipment that are rated for ever higher amperage, should have ever better cooling systems, to offset the load, rite? Of course, nobody wants a big heavy power tool, and manufacturers want their products to sell…thus, we now have 4 ½” angle grinders with 9.2 amp motors in them (one model boasts 12 amps); these would have been found in 9” angle grinders, back in the nineteen fifties. Has there been a magic upgrade in electric motor manufacturing since then? No; “compact” electric tools simply heat up fast, and need to be used intermittently; the higher the amperage rating for your little grinder the smaller its duty cycle (the amount of time it can be run, in any ten minute period); or else buy a big grinder to do the job. It's not a magic wand, Harry; it's just a power tool.

Angle grinders are the faster tools for cutting the metal parts needed to build forges, and the air/fuel burners that heat them; while rotary tools (or die grinders) are more precise tools for cutting and shaping the small parts, which burners are made from. There is a lot of cross over between both kinds of work, and therefore between what tool does what task best. In the grand old tradition of "wanting our cake and eating it too," we like to find ways to extend the usefulness of both tools; I hardily agree The main obstacle for doing this easily is that rotary tools tend to have too little power (thus, we look to electric die grinders), and angle grinders mostly have way too much! One more reason to keep that grinder "under powered." So, by starting with a 4-amp grinder, and including a fan speed controller to its power cord (always avoid using the inbuilt speed control circuits on power tools, if you want them to last), You can safely use that grinder for all manner of metal cutting, and grinding tasks, which would otherwise be most unwise. Such as what, for instance? Such as mounting a small extension spindle and/or converter chuck, and using rotary accessories, in what will then amount to an angle head die grinder.

The G LAXIA 4 amp angle grinder is the first small angle grinder that I've seen with this low an amperage rating, since Makita first marketed their 4" angle grinders about forty years ago; since then, every new model angle grinder has boasted more, and ever more power. So, why would anyone want a wimpy little 4 amp grinder, anyway? To be able to cut steel parts, in reasonable safety! The joy of this deal is that this grinder only costs $27 on Amazon.com; it even has fair costumer reviews

Avoid overheating your torch-head It is popular to use small propane torches in two-brick and coffee-can forges; as an introductory move to metal work, this makes since. However, when more heat is desired, propane canisters are often replaced with propylene, and greater caution is required. Nearly all torch-heads that are rated for use with both propane and MAP gas (actually propylene fuel gas since 2008) have the same warning about not turning the torch flame down too far; to avoid overheating its flame tube. Increased fuel flow, induces added air. This air/gas mixture is all that cools the flame tube; which makes sense, once you realize that the incoming air is mixed with gas that has been greatly chilled by expansion from its liquid state (refrigeration effect). But, when the flame tube is placed in super-heated equipment, like a forge or furnace, overheating problems can increase; it’s something to keep in mind before cutting back your gas pressure to save fuel. The more its flame is reduced the less super-cooled gas/air mixture that is passing through the torch-head's flame tube, at any given time. But the heat retaining layers of insulation surrounding that tube, in the portal, will rapidly accumulate very high temperatures, despite the flame being turned down. So, it is prudent to keep the refrigeration effect from the incoming fuel/air mixture turned up high; especially during longer heating cycles. The safest plan is to locate the end of your flame tube just inside of the equipment’s steel shell, and create a slightly tapered (expanding) opening, with cast refractory, between the shell and the forge interior’s flame face. While fine for use in brazing out in the open air, take care if using propylene inside forges and casting furnaces; unless your burner is undersized, such confined spaces will get too hot for many refractory materials; propylene flame temperatures can easily melt a stainless-steel flame retention nozzle inside heating equipment. Refractory flame retention nozzles are a better idea than stainless steel with propylene fuel, unless the equipment is only going to be run, as a hand torch, out in the open air. Note: Most commercial dual-fuel torch-heads have a thin wall stainless steel flame-tube, which ends in a bull-nose shape at its gas opening; this serves a similar purpose to what we call the mixing tube and flame retention nozzle on a propane burner.

Flame retention nozzles The first question to ask, is do you need one, if your burner is placed within a forge; probably not. Do you want one? Definitely. Because your forge will most likely run just fine without a flame retention nozzle mounted on its burner, why bother? Well, some people don't bother with one. However, if you have no flame retention nozzle on your burner, I hope you at least screwed a pipe coupling over the end of your burner's mixing tube; otherwise the mixing tube itself will start oxidizing away, within the forge. The point of all this is that you have plenty of time to provide the burner with a flame retention nozzle. I see lots of pipe reducers being employed as nozzles; if your reducer ends up a little too large, a short piece of stainless steel pipe or tube can be held within it, with a stainless steel socket set screw. Be sure that the screw is stainless. Mild steel will become stuck in place, after a few heats. Moving the short piece of pipe or tube forward or back within the reducer will change its width to length ratio, just as effectively as moving the position of the outer tube does with a slide-over step nozzle; allowing you to fine tune burner performances, in the same way. Once again, this improvement does not have to be done right away.

Or, maybe it would work better to hear an evaluation

What do you think about the new Diamondback forge line? Since there have been major changes in the construction of Diamondback forges, it would be nice to here an evaluation of them from anyone who has purchased one of the new models; especially if they had previously owned or used one of the old models. Aside from the change from ceramic board to ceramic wool, I don't expect to hear about any other significant differences, but we never know, do we? As to the different insulation; yes it is a down grade. However, it is far more than matched by the reduction in prices, allowing many more beginners to buy a dependable gas forge, and upgrade back to ceramic board, later on. I would only be concerned if purchasers did not consider the rest of the forge construction, to be as solid as the old models.

The burner's mixing tube; your second chance So, if you want to use a threaded pipe reducer, are you kinda out of luck? Nope, you can still get up to a 2.5 to 1 constriction ratio; it just takes an added step or two. The best news is that, if you already purchased a badly designed burner, it can be improved, in just a step or two If you internally bevel a short length of schedule #40 pipe (standard water pipe from the hardware store), and screw it into the reducer fitting, that reduces its internal diameter about 1/4". If you use schedule #80 pipe, the reduction is about 1/2". Be sure to bevel that pipe end, so that the internal conical shape is not interrupted! Now drill and thread one or more screw holes through both the pipe fitting and the spacer you have just screwed into it, so that the mixing tube, which is also to be internally beveled, will be held firmly in place, after being pushed into this collar. If you use the next size smaller pipe, it will need to be power sanded a few thousangths, to fit into this area. But, how long should the mixing tube be? Too short, and the gas will not completely mix of with incoming air. Too long, and it slows down the mixture's flow speed into the flame retention nozzle, weakening performance. Although it will very, depending on burner design, between eight and nine times the tube's internal diameter, generally works out quite well on naturally aspirated burners. So, start at nine diameters, and cut back a 1/4" at a time, to reach optimal performance. But, what about existing burners? Cut off the mixing tube, even with the end of the pipe reducer. Next, cut the off the flame retention nozzle, even with the mixing tube. Drill and thread one or more holes in the flame retention nozzle, and in the pipe reducer, to slide the next smaller mixing tube into; remember to cut the new mixing tube at nine times it internal diameter, to begin with. Won't you need a smaller gas orifice for a smaller mixing tube? Perhaps, but my experience has been that nearly all those cheap burners had oversize gas orifices, anyway. If, not, push a short piece of syringe needle into the existing gas orifice, to make it smaller. If the the part used for the burner's gas orifice permits, its hole can be enlarged and threaded for a 3D printer nozzle, if you do not care to fool around with needles, are capillary tubing.

Air entrances on linear burners So, just what advantage is gained in a burner from from a conical shaped air entrance, such as a pipe reducer fitting, on a linear burner? Mainly, increased mixing of incoming air with the fuel gas. Propane takes a fair amount of mixing to burn completely in a primary flame envelope. A swirling motion provides the most mixing for the least drag on your burner’s air-gas mixture flow. Any device that provides lateral air movement at the burner’s air opening, will boost swirl through its conical shape; this includes the openings on “T” plumbing fixtures (whose opposed inlets create swirl at the opening of the smaller central outlet (the conical restriction created within this outlet, then increases that swirl); disc shaped choke plates near funnel entrances (which force incoming air to change direction at the air entrance (starting a swirling motion at the lip); or fan blades placed at a funnel’s entrance (which deflect the direction of incoming air laterally, starting swirl at that point). All this redirection of air trajectory is minor, but it creates the right vector at the starting point of air movement. It takes no more energy to induce air laterally, than to induce it straight into the burner’s air opening; less energy is then needed to redirect speeding air molecules within the conical shape; thus, providing a boost to rotation. So, we see how disc shaped air chokes on the entrances of modified pipe reducer fittings got their start; they do help create swirl, but why would they be needed? Because those air entrances, which were especially cast for this purpose,used existing pipe reducers as their models. Unfortunately reducer fittings for water pipe tend to have two to one or smaller constriction ratios. Anything less than a two and one half to one ratio is insufficient; three to one constriction ratios are better. This is why I avoid threaded pipe reducers for linear burner air entrances.

The burner flames in the photos are both seen to be reducing, because of their green tinge; yet, they have a nice shape, and the secondary flame envelope is quite short...I would say that you might try shortening the amount of overhang in the flame retention nozzle, past the end of the burner's mixing tube. If that does not improve the flame color, than "if it ain't seriously broke, don't fix it." Yes, I remember the discussion of "the accidental twist." Thanks for sharing your photos; they always help others to come up with new ideas.

I thought that you might need some advice on how to employ a commercial propane torch-head properly, but It sounds like you are right on track. Any photos of your burners? We love photos

Jono, I hear you loud and clear, mate. It was the desire to avoid standing in front of something like a blast furnace that started me on this journey, in the late nineties. The last job I had before the little woman retired me was with a metal artist. He had built a fan-blown natural gas forge that heated up a large commercial building to the point that we had to open the truck door in the dead of winter--ugh! What are you employing for a burner?

Those are all excellent questions, and fortunately they have practical answers. To begin with, the difference between good enough and best performance in your forge's insulation diminishes, along with the size of the equipment. So, using straight refractory in such a small forge, rather than complicated insulation layers is only a very small no-no Better yet, that refractory can be made pretty insulating with the addition of silica or high alumina spheres in its mixture; these should be available through a supplier of concrete, as lightening concrete is what they were invented for. Best of all, the addition of Perlite, a common soil additive will do a similar job. I recommend a smoothing layer of straight refractory over the layer with Perlite; smooth is very good for heat reflection from flame faces This being so, then why do I go on and on about how to do things the difficult way? Because I'm a picky-butt BTW, the formula would be one-third Perlite by two-thirds refractory. That is by volume; not by weight.

Fine tuning heating equipment Fine-tuning burner performance completely is usually done while running it in its intended equipment, and only after adding finish coatings, and a front baffle plate, door, or brick wall for an adjustable exhaust opening to the forge and/or furnace, along with adjustable secondary air chokes installed on burner mixing tubes. These things are needed to raise internal temperatures high enough to ensure complete combustion. Sounds backward, doesn't it? But the thing is that perfect performance only comes in equipment that has been turned into a radiant oven. Even as the burner’s flame is best judged in a cold forge, final evaluation of the burner’s effects in the forge, is judged by looking at the exhaust, and the level of incandescence on internal surfaces. The burner is merely part of the forge; if performance only revolved around the burner, most of what we have learned about constructing heating equipment would be "gilding the lily”—It is not. Back when I was still writing Gas Burners for Forges, Furnaces, and Kilns, I raised the temperatures in my first forge enough that it changed from orange to lemon yellow incandescence, merely by refining the high-emission coating it was painted with (by separating crude particles from its colloidal grade particles, using water). A few weeks later, lemon yellow jumped up to yellow white by stopping all secondary air from entering the burner port; this can be further refined with the addition of a sliding secondary air choke on the burner's mixing tube, and a baffle wall in front of the exhaust opening. It has been stated that good burner performance is a delicate dance of different forces; ditto for the equipment it heats.

Coffee-can forge/furnaces There seems to be some confused ideas about coffee-can forges being a cheap and easy way to get into blacksmithing. What they are is an economical way to forge small parts, once the forge is built. C-C forge construction also provides some economy 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. Castable refractory can be purchased in five-pound bags, economically providing good flame faces to protect the ceramic fiber insulation; these make smart choices; but the most significant savings come from minor fuel consumption; their use in casting furnaces preceded their use in miniature gas forges. This equipment is compact, making it highly portable, and handy for those with limited space; jewelers, can use it to forge chasing tools, or small hammers, and then employ it as a small casting furnace. This combination of forge/furnace is also handy for makers of upmarket folding knives, and other small metal art objects. Primary insulation layers made of mixtures of Perlite and water glass (sodium silicate) are going to melt in short order, if you heat your forge up to yellow incandescence; only employ perlite and sodium silicate in tertiary layers of insulation, with ceramic wool or insulating bricks between it and, a primary layer of castable refractory. Perlite and furnace cement will break down more slowly, but they still cannot hold up to direct flame impingement. You could mix Perlite and castable refractory as a secondary insulating layer, but then you would have spent enough money to buy that square of ceramic wool blanket; there isn’t much economy in that move. The infamous plaster and sand 'refractory formula' is such a major heat sink that you will want to throw your forge in the garbage, before this so-called refractory even has a chance to crack apart! The second “cheap and easy” idea about C-C forges is that you can simply run them with canister-mount torches. There are high priced dual-fuel (meant for propane and propylene) torch-heads that have stainless steel “flame tubes”, which are so thin that they quickly oxidize away in the super-heated environment inside of a forge. Most propane torch-heads have brass flame retention nozzles, which will melt inside of a forge. So, the torch cannot be placed in a sealed burner port. Instead, it can only be placed in an oversized hole, if its flame is weak enough, or aimed toward the hole from outside of it, if it is one of the hotter burning models. Either way the torch’s flame nozzle is either destroyed, or must be used inefficiently; the usual answer for this problem is to replace propane with propylene fuel canisters, at twice the price, to provide sufficient heat! A better choice is to push the thin-walled stainless steel flame tubes, of dual-fuel torch-heads into a thicker walled stainless steel tube, to slow down high heat oxidation losses, and to leave a flame retention nozzle in pace, after the inner thin layer is mostly oxidized away. This configuration can be placed into a forge’s burner orifice. To prevent oxidation losses on the original nozzle’s outer surface, this spacer tube must be interference-fit into the stainless steel flame tube; no air gap between these two parts can be permitted; this also has the advantage of maintaining the outer tube in place, after high heat oxidative erosion has done its worst on the thin layer’s inner surface. All of these thin flame tubes have narrowed openings, which are needed to maintain a flame; this area will oxidize away quite rapidly, when placed within a forge. So, an additional short outer tube is added, creating a full-fledged flame retention nozzle, and the bull-nose end of the flame tube is cut away, as it is no longer needed, or desirable. The better commercial torch-heads have screw on torch tips, eliminating the need to cut away the bull-nose section of their flame tubes, and permitting them to continue being used for delicate heating tasks. If you are going to all the trouble to build a burner, or repurpose a commercial torch-head (and you certainly should), you will want to place it in a forge that is worthy of it, right? Now you have another consideration, because a 3/8" burner is the largest size you can use in a coffee-can forge; by the time you have constructed it, you might not want to place such a nifty little burner in a tin can forge. So, you may decide to spend a little extra, to use a stainless steel container. 3 lb. coffee-cans (used for years as coffee-can casting furnaces, and later as forges) are about equal in size to 1 gallon paint cans (these are 6.6” diameter by 7.5” long), or #10 food cans (which are longer, but narrower), or some of the four-quart, or even five-quart, stainless steel containers; this last is the choice that is being recommended for forge/furnaces. Of course, a stainless steel stock pot, or kitchen canister is far stronger than any tin can; able to support exterior parts from, and will last forever. You can search for likely containers by imputing “stock pot” or “stainless steel canister” into your search engine. A nu steel 4qt stainless steel canister is a perfect size and shape for a Coffee-can forge; it is as long as any coffee can at 7-1/4” and a little larger diameter at 5.9” outside diameter; available through Amazon.com. Oggi Stainless Steel Kitchen Canister is 5-quart size; it is 8” in diameter and is 8” high, including an air tight locking lid, which saves a lot of work, since its clear plastic section can be replaced with hard refractory, and turned into a proper lid for a casting furnace, and forge door. The added twenty percent of interior space, combined with the existing lid mechanism more than repays its price of $25.49 through Amazon.com. 6-quart Stainless Steel Canister is 9.2” long by 7.4” diameter; its extra length and diameter makes it a very handy improvement over the standard 4-quart containers normally used in coffee-can forges and casting furnaces, as its extra length is perfect for mounting two 1/4” burners; it is available for $29 through Amazon.com. The main difference between a tube forge and a casting furnace is that the forge lays horizontally, and the furnace stands vertically. With a little added work on its legs (to keep it up above sand box level in casting mode), along with the addition of an emergency drain hole in the bottom face to let liquid metal escape into the sand in case of crucible failure (or a second crucible for gold or silver), and a door in front/on top, which moves out of the way; a forge/furnace can be made to do both tasks quite well. 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/lid and the forge floor; the larger the forge, the more serious these limitations become, but in a coffee-can forge/furnace the limitations are minor, because its forging capacity is limited to begin with. Thus, the lack of a flat floor section presents little inconvenience. Of course, a separate flat section can be cast, and placed within larger forges, for heating stock, and removed during casting. Another limitation in forge/furnace design is burner positioning. While the flame can be pointed in several ways within a forge, the flame in a casting furnace is aimed to impinge on the furnace wall as far away as possible, without impinging on the crucible (since flame impingement on a crucible promotes cracking). If the flames in a forge were aimed this way, they would not burn for a long enough distance before impinging on work pieces, if the burners should be pointed downward, toward a floor area. In these days of greatly improved castable refractories, it is better to aim them up and slightly inward, to ensure the longest possible exhaust path before impingement on work pieces, while also keeping the full force of a flame from impinging on crucible walls. When the forge doubles as a casting furnace, the use of two burners changes from a smart choice, into a practical necessity; this allows the burner toward its rear to be run alone, while the forward burner (which now becomes the top burner), is shut down, rather than wasting some of its heat (it being positioned too high on the crucible for efficiency). But that single burner needs to provide enough heat to do the job; thus, for bronze casting, you may want the rear burner to be 3/8” size; not ¼”. The larger burner can always have its gas pressure lowered to reduce its flame down to the equivalent of a ¼” burner for forging. Surprisingly, 3/8” burners are much easier to build correctly than ¼” burners; this is mainly due to the gas orifice. The smaller the gas orifice the greater the difference between a desired diameter and what may be available at any given time. All the other differences between what is optimal and what is available in part dimensions become exaggerated in miniature burners, too. But, the lack of exact gas orifice diameters is the chief restraint to building ever smaller burners; can it be done? Yes. Is it worthwhile? Probably not. If you use a 6-quart size stainless steel canister, that 3/8” rear burner can be used to full effect, when forging.

Rose, We on IFI are aware of the feeling of "information overload" in beginners. However, once you get started, do not hesitate to refer back to us for metal smiting information, once you wade down to the deep end; we've all been there

The RimCereal 6-quart Stainless Steel Canister is 9.2” long by 7.4” diameter; its extra length and diameter makes it a very handy improvement over the standard 4-quart containers normally used in coffee-can forges, as its extra length is perfect for mounting two 1/4” burners. It is available for $29 through Amazon.com.

At these low low prices, what about a two burner forge? I would say, go for it, because you can always divide the interior space, by placing a brick between the burners, leaving one shut off. Well, if two burners are better than one, than why not three? Because of back pressure, ruining burner performance; this will force you to open that long side panel...

Diamondback forge update For years, I have suggested single burner Diamondback forges to people who don't want to spend the time to know what they are doing, before building their own gas equipment; that hasn't changed, but the forges they offer certainly have; mostly for the better...mostly. To begin with, they seem to have lowered their prices, while everyone else is raising theirs! There have also been structural changes to the forge bodies, which I consider as clever, and not harmful; they seem to have increased the amount of bolts and eliminated all welding--good! They also look to have changed away from ceramic board insulation to ceramic wool--BAD! However, you can update your insulation back to ceramic board, once the wool wears out. They offer a three burner forge, with an open side panel; the original use for this feature, was heating horseshoes. If you're not a farrier, the usefulness of a side panel, is likely to be more apparent than actual; however, other forges that have this kind of third opening have problems with warping of the forge body, which is very actual. Its up to you. I'm just saying...

And Kast-O-lite 30 is sold in five pound bags by several sources, for just this purpose.

Yes, their burners do work well. I would not want to leave the impression that they are not sufficient. Of course, being such a picky butt, I will always want just that little bit more...