Mikey98118

After the burner portal tubes have been installed, it becomes time to install four individual legs, to hold a forge up a few inches above whatever surface it is sitting on. Another four legs need to be added at the rear face of forge/furnaces to hold the shell well above the sand filled steel pan, that it sits on, during casting. Or, build a carriage made from a bent 3/16” steel rod, which does the tasks of both sets of legs. Building the carriage is no more work than drilling eight holes and mounting eight long bolts in the equipment shell. All it requires is: (1) A nine foot long 3/16” steel rod. (2) Eight 10-24 nuts. (3) A 10-24 die to run threads on the rod ends with. (4) Two vice grip pliers to bend the rod into various right angle turns with. after heating it to red heat with one of the equipment’s burners. (5) A 3/16” chainsaw rotary file, to prepare the ends of two braces for silver brazing. (6) Silver braze filler and flux. Since you are just silver brazing on mild steel, 45% silver content and white borax based flux is fine for this job. Find the center of the rod, and make a mark 6” on either side of it. Heat and bend the rod at right angles at each mark, creating a “U” shape. After it cools, sit the “U” shape on a flat surface. Heat and bend down whichever leg of the “U” is raised up out of a flat plane. Make a mark 16” down each leg of the “U” from the cross bar. Heat and bend each leg up at right angles. Now, make a mark at 12” down each leg from the bends you just made. Heat and bend each leg up again. With the carriage lying flat between the second and third set of bends, so that the first “U” and the two ends of the legs are pointing up, lay books or boards in place to support the forge/furnace shell about 4” above the rods, and next to the shell’s open end. Male sure that the burner portals are positioned correctly, before going any further. Heat and bend the rod ends inward at an angle toward each other. and mark where you want to drill two holes for the forward end of the legs to penetrate the shell, after the excess material is cut away from them. Move the shell over beside the books or boards, and place first one mark, and then the other against the corner of your pile; mark a line down the from where the front holes will be, to the bottom of the shell, make cross marks 1-1/2” from the bottom face, to mark where the rear holes will be. Drill all four holes, and replace the forge/furnace back on the pile. Mark legs a little long, and then cut off the excess rod ends. Thread the end of the legs for a distance of 1-1/2”, and run a nut all the way to the end of the thread. Then, heat the bends in both legs at the same time, and re-bend them so that they slide through the holes. After the carriage cools down, screw a nut unto the end of each leg, and then screw the outside nuts up, as tight as it will go against the shell. Now, thread the two cut off pieces of rod the same as you did the two leg ends. Run a nut on each one of them a little further down the thread then is needed to allow sufficient thread for the inside nut, and push them, one at a time, through a rear hole, and swing them up against the carriage, make a mark for cutting that will leave an extra 1/8” or more of length, and cut off the rest of the excess on each piece of threaded rod. Now grind a round groove, using a 3/16” chainsaw rotary file into the ends of the rods, so that they will stay in place, without a gap; trapped between the carriage and shell, during silver brazing. Flux each joint, heat, and silver braze the two braces in position. Screw on the inside nuts, and screw the outside nuts tightly against the shell.

I agree with Frosty. If it was just a simple cylinder shape, you could get away with heating it up as is. However, you have three different hard right angles in this casting, which is not advised. Thus, you don't want to press your luck any further.

The burner ports are placed at a third the distance from the forward (top) opening, and rear (bottom) face of the forge/furnace; they consist of pipes or tubes large enough for the burner’s flame retention nozzles to pass through easily. Six socket set screws are screwed into them in two circles of three equidistant places. This arrangement secures them in place, and permits minor adjustment in aiming. Socket set screws are employed, rather than wing screws, so that the screws can be adjusted even when hot. Lots of people just use hex bolts, but that requires the use of a wrench. A small Allen wrench is easier to employ, and you while probably need this wrench to adjust the burner, anyway. By using the same size socket head set screws on the forge/furnace as used on it burners, the number of tools you must purchase is reduced. The next question is how to secure the burner ports to the forge/furnace shell. Stainless steel cannot successfully be welded by anything but welding rod or wire fillers dedicated to this task; welds made with the wrong steel alloy will crack, sooner or later. So, braze welding (which requires an oxy-fuel torch for most), silver brazing (which does not tolerate gaps over 0.005”), or silver soldering (which can bridge some gaps with expensive filler alloys), are your choices, for thermal joining; each choice has its limitations. However, the burner port tubes can be screwed onto the shell. You start by cutting a hole for each burner portal in the equipment shell, with a hole saw. Next, the pipe or tubing that is later to be cut into burner portal tubes, is placed in a hole, and a short line is marked on the shell, at it top and bottom areas. The tube is removed and a 1/16” elongation is ground into both areas. The tube is replaced, so top and bottom lines can again be marked on the shell; then another 1/16” is ground away. Repeat this operation, gradually changing the opening from a hole into an oval shape; this allows the burner portal tube, to be aimed at any desired angle, while maintaining very close tolerances between shell and tube. Once you have determined that the angle is optimal, the opening is ready to receive a burner portal tube. At this point you must decide to silver braze, silver solder, or screw the portal in position. If you opt for thermal joining, cut the tube along this first line, and proceed to use the tube’s other end to prepare the shell and tube for the second burner portal. If you opt for screwing, slide the tube into the opening 1” deep at the top of the tube or pipe, and ink mark the tube where it intersects the shell. Also mark a longitudinal line on the portal tube, with a matching line on the shell. Repeat this process on this tube end’s bottom area. Now, mark a second line where the tube and shell meet. Remove the tube and mark cutting lines on both sides of each longitudinal line on the tube. Cut into all four lines from the tube edge to where they meet the shell’s matching outline. Then, cut away the oval lines between the four longitudinal cuts, and remove the two portions of pipe or tube, leaving a tab at the top and bottom of the portal tubes. After the portal tubes are cut to length, these tabs will be bent, to match the angles of the shell, and the portal tubes will be pushed into position from the inside of the shell. The top and bottom lines on the shell show you where to drill holes screws, which will hold the burner portal tubes tightly in position against the equipment shell.

This is the main reason for running two 3/8” burners, rather than to two ¼” burners. The larger burners can be turned-down for forge work, while a single 3/8” burner can be turned up enough to heat gold or brass well into pouring temperatures. Surprisingly, 3/8” burners are much easier to build correctly than ¼” burners; this is mainly do to the gas orifice. The smaller the orifice the greater the difference between a desired orifice diameter and what may be available. All the other differences between what is best and what is available in part dimensions become exaggerated in miniature burners, too. But exact gas orifice sizes are the central aggravation.

Printer Nozzle Gas Orifices The gas orifice on a naturally aspirated burner must closely match its diameter in relation with the diameter of the narrowest point of constriction, no matter what the inside diameter of a burner’s mixing tube is. On 3/4” and larger burners, this is best accomplished with a MIG contact tip. On burners 3/8” size and smaller, 3D printer nozzles have every advantage over MIG tips (even with capillary tube trapped in them as precise gas orifices); this is because the greatly increased friction of the gas molecules through smaller orifices make it necessary to shorten the length of capillary tubes down to that of printer nozzles. So, in smaller burners, capillary tubing used for gas orifices give little advantage, while printer nozzles are cheaper, more easily acquired, and far simpler to mount. Right in the middle of these ranges are 1/2” burners, which can benefit from a correct size and length of capillary tube in a MIG tip, but with printer nozzles do nearly as well (with less work and expense). MK8 Ender 3 extruder nozzles are available through Amazon.com); they have M6x1 male thread. The markings on each of these nozzles stands for the orifice diameter in millimeters: 0.3 (millimeter) is 0.0117” orifice diameter is a good gas orifice size on a 1/8” burner. 0.4 (millimeter) is 0.0156” diameter is a good gas orifice size on a 1/4” burner. 0.5 (millimeter) is 0.0195” diameter is a good gas orifice size on a 3/8” burner. 0.6 (millimeter) is 0.0234” diameter is a barely workable gas orifice size on a 1/2” burner. 0.7 (millimeter) is 0.0273” orifice diameter is a suitable gas orifice size on a 1/2” burner, but a capillary tube can be tuned for performance by varying its length; thus, the right orifice diameter capillary tube can give a little better performance than just a printer nozzle. Printer nozzles generally have M6x1 thread, but there is another difference to look for; they have grown longer. The latest models feature 5/8” of thread length; this is important, because you need the gas orifice to run parallel to the axis of the gas tube. The older printer nozzles had as few as three threads, which were far harder to ensure a proper aim with.

Coffee-can forges 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, after the forge is built. C-C forge construction 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; these still make smart choices; but the significant savings come from minor fuel use. This equipment is also highly portable and compact, for those with limited space. For jewelers, they can be used to forge chasing tools, or small hammers; and also employed as a small casting furnace. Primary insulation layers made of mixtures of Perlite and water glass (sodium silicate) are going to melt in short order, if you heat the forge up very far; only employ perlite and sodium silicate in tertiary layers of insulation, with ceramic wool between it and, a primary layer of high heat castable refractory. Perlite and furnace cement are going to break down more slowly, but they still cannot hold up to direct flame impingement. You could mix Perlite and castable refractory as a secondary insulting layer, but then you would have spent enough money to buy that square of ceramic wool blanket. The infamous plaster and sand 'refractory formula' is such a major heat sink that you will want to throw your forge in the garbage can, 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 retention nozzles, but those nozzles 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 side 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 is either destroyed, or is under powered; the usual answer for this problem is to replace propane with propylene fuel canisters, at twice the price! A better choice is to push the thin-walled stainless steel flame retention nozzles, of dual-fuel torch-heads into a thicker walled stainless steel tube, to protect them from high heat oxidation losses. Then place the protected flame retention nozzle into a forge’s burner orifice. To prevent oxidation losses on the nozzle’s outer surface, the flame retention nozzle must be interference-fit into the stainless steel tube; no air gap between these two parts can be permitted. If you are going to all the trouble to build a burner (and you certainly should), you want it placed in a forge that is worthy of it, right? Now you have another problem, because a 3/8" burner is the largest size you can use in a C-C forge; by the time you have constructed it, you will not want to waste it in a cheaply built tin can forge. So, you might decide to spend a little extra to use a stainless steel container. 3 lb. coffee-cans (used for years as coffee-can forges, and by others as casting furnaces) are about equal in size to 1 gallon paint cans, or #10 tin cans, or some of the taller four-quart stainless steel kitchen pans. 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 (to keep it up above sand box level in furnace mode), 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 door that revolves out of the way, 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 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 capacity to heat work pieces for forging is limited to begin with. Thus, the lack of a flat floor section presents no problem. Another limitation in forge/furnace design is burner positioning. While the flame can be pointed in several ways in a forge, the flame in a casting furnace is aimed to impinge on the furnace wall as far away as possible, without directly impinging on the crucible (since flame impingement on a crucible promotes early failure). 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 the floor area. In these days of greatly improved castable refractories, it is better to aim them upward and slightly inward, to ensure the longest possible exhaust path in forges, while keeping the flame off of any crucible’s wall. Also, the use of two burners will change from a smart choice into a practical necessity, when the forge doubles as a casting furnace; so that the burner toward its rear can be run alone while the forward burner, which now becomes the top burner, can be shut down.

Have you asked them directly?

You're welcome, Frosty.

Nah; you can't walk away with a line like that! Tell us about those burners

That was when I started calling it "the magic flame" in my mind. Because, in his mind it was magic. Before, such flames were just business as usual. So, he taught me more than I taught him

15/16" cutoff discs Until recently, 1-1/4" cutoff discs were the smallest steel cutting discs that were commonly available. Dremel #420 15/16" discs were the only steel cutting discs available in this small diameter. All other 15/16" cutoff discs were the thinner garnet red discs, which are used by jewelers for cutting gold and silver rings. However, 15/16" steel cutting discs are becoming standard in accessories kits now. How to tell the difference? Steel cutting discs are dark gray. Jewelers' discs are garnet red, because garnet grit is what they are made from.

I bought mine through Amazon.com; they are no longer offered there. I think they woke up about what a how undervalued they were, and withdrew them

Well, as "an old hand" on this subject, I find that moral support means a tremendous whole big lot for beginners Twenty years back, I had a "class" or four people who wanted expert help to build very hot gas forges, run by extremely hot burners. One of the four was an airline pilot; he was far from a mental slouch. Yet, even when confronted by the other three having built successful burners, with perfect flames, he could not believe that he would; I think it was a question of wanting to succeed too much. The closer he came to completing his burner, the more he didn't believe that his burner would work, just like everyone else's did. Finally, the day came for him to light it up...and it worked perfectly. You should have seen the grin on his face! Lesson learned; moral support is as at least as necessary as as correct information, for beginners.

Scoring and parting burner tubing I previously recommended Rigid's miniature pipe cutter, as being the best choice available; well that was then, and this is now. A bunch of new pipe cutters are being offered on Amazon.com these days. The Saillong Mini Steel Tube Cutter (No. 174-F), with two spare cutter wheels and “E” spring retaining clips, are now recommended for tube diameters from 1/8” to 1-1/8” (3-28mm); it is used for parting copper, brass, aluminum, and thin stainless steel tube (up to1/16” thick); $10 from Amazon.com. This cutter is not a necessity, but is quite handy, both for parting the mixing tube, and for scribing perpendicular lines, (for cutoff discs) in the larger tubes or pipes chosen for flame retention nozzles in 1/4”, 3/8”, and ½” burners. This is the best quality I have found in a miniature pipe cutter, and yet it is offered at a low price. Unlike my Rigid pipe cutter, the No. 174-F cutter wheel tracks perfectly (no wobble), and so it takes no special care to maintain a single cut line in the material, rather than fighting a tendency to leave a spiral score on the material, instead of immediately starting a proper cut.

Go-to tool for burner construction I may very some of the tools employed to build very different burner types, but a rotary tool is used on every one of them; a separate rotary accessories kit is highly recommended. If it comes down to a choice between buying a drill motor, or a rotary tool, go with the rotary tool. The cheap tool kit that comes with many rotary tool offers, will barely be able to successfully complete the work on one little burner, and those cheap accessories will not be pleasant to deal with. Much better accessories kits are offered through Amazon.com. I suggest the Populo 305 accessories kit, which has decent quality, and is only $15.90. Or, you could invest about the same amount of money on a Dremel EZ406-02, EZ-Lock Starter Kit, which includes their EZ–Lock mandrel, and four 1-1/2” cutting discs; this will do the best job of cutting pipe and tubing, which is where cheap accessories included with most rotary tool offers fail badly. So which choice is better? If you are a novice with rotary tools, I suggest going with the Dremel option, as you will need far more help with cutting than any other task (and their special mandrel is serious help). Note: Some people have found that the sheet metal hub on one or more of their EZ-Lock cutting discs separated; if this happens, stop immediately and remove the disc. Use hardening thread-locker to glue the hub back onto the disc, and clamp it; then wait twenty-four hours for the glue to set hard, before using the disc again.

What you should know about speed controls (1) The first rule for speed control, is do not attempt to adjust speed while a tool is engaged; move it away from the work surface first. (2) It is a popular marketing ploy to include inbuilt speed control circuits on compact equipment, such as rotary tools; avoid their use like the plague. If you end up with a variable speed tool, just leave its inbuilt controls on high (in effect, not engaged), and employ a separate router or fan speed controller (for brushed motors), or a brushless speed controller (for motors without carbon brushes). Plug the right type of speed controller onto your tool’s power cord; it will do the job, without any risk of overheating the equipment’s delicate speed circuit, and shutting down the tool, until the burned-out circuit can be bypassed. Speed control circuits on the very cheapest power tools just use potentiometers (variable resistors); as in heavily power robbing. A modern variable frequency drive slows the number of pulses per second in the right kind of DC motor (which is found on most hand-held equipment these days), but not the amount of power in each pulse, so it’s drop in torque is comparatively minor, as motor speed slows. Many of the cheaper inbuilt speed controls are erratic, and give poor control in their bottom range (or none in some settings), long before they fry. Dremel mounted the first speed controls on rotary tools; they were cross-slide types. This was and still is a hardier design then the tiny inbuilt circuits on other tools. Dremel has kept these controls low priced, easily available, and plug-in on their oldest rotary tool models; none of which is true of the speed control circuits on their new models. The Dremel #100 has a sliding on/off switch. The #200 model uses a sliding combination on/off switch and speed control; these switches are interchangeable. You can use an external speed control on a #100 because it’s sliding switch only turns the tool on and off. But don’t use a separate speed control on the #200, because they warn that it will mess up that model’s own speed control circuit. (3) Even with external speed controllers, do not run motors below half-speed for very long, to avoid overheating their windings (ex. just long enough to drill a single micro hole in pipe or tube). (4) You can still overheat the motor by bogging it down under a heavy load; even on full speed (and faster on reduced speeds), but it happens slowly enough for the heating motor housing to give warning, in time to let the armature windings cool off. But, overheating an inbuilt control circuit happens suddenly. Your first warning is usually a dead tool, and then you may notice a little smoke…or not. (5) The faster you race a gasoline engine the hotter it gets; it’s natural to expect that about electric motors too; but the opposite is true. As you slow an electric motor down, it heats up. (6) Flex-drives complicate motor heating problems, because the faster you run them, the hotter they get. Foredom Tool’s top of the line KTXH440 is set up to run between 500 and 15,000 RPM; these are, by definition, the best of the best. How can we expect a Chinese import freebie to last at 35,000 RPM? So, you have competing needs with a flex-drive mounted on a rotary tool. What to do? Run the tool at half speed, in short bursts to let both drive and motor cool down; use it no more than you must. Does this sound inconvenient? What part of flex-drives don’t belong on rotary tools didn’t you get? If you blow a control circuit, do you have to throw away your tool and buy another? That depends; if you are into electronics, it is simple to de-solder the circuit and replace it with a short length of wire. If not, it is still simple, but you will have to buy a soldering tool, some rosin core solder, and some electric wire of the same gauge (size) or larger than what was used in the circuit; the cost will be about equal to replacing the tool, but you’ll end up with a repair tool out of the deal. Your “fixed” tool will only run at full speed, unless you use a separate speed controller, but that is what you should have been doing in the first place. The separate speed controller can also be used on many other tools. Speed controllers for brushless motors: Most speed controllers are designed for motors with carbon brushes (brushed motors). Brushless motors (BLDC) need brushless speed controllers; they aren’t hard to come by, or expensive. But there are no plug and play versions available for hand tools; at present they’re only available as kits. The easiest kits to deal with have all the electronics contained in a perforated metal control box, to which you must add electric cords and/or wires; one set incoming from your power source, another outgoing to the tool; wire a receptacle to it (if you want to plug in two different brushless tools at once), or use the last few inches of the extension cord you probably just cut off to make a lead to the power source. The RioRand 7-70V PWM DC Motor Speed Controller Switch 30A is available through Amazon.com; it has four terminals for wires to mount on; negative and positive “input” terminals from the power source, along with negative and positive terminals “to motor”; they are all plainly marked; there is a speed control dial on the side of its perforated metal body. Why metal, and why perforated? For heat dissipation. Black wires go to negative and red wires go to positive on this brushless motor speed controller. When the armature fries: If you see smoke and electrical sparks coming from a tool’s air vents, you just overheated its armature for the last time. If replacement parts are available for your tool, you will easily find them online. Just input the product name and add “parts list.” You will need another armature assembly, and a new set of brushes. These parts are available for the Dremel #100 & #200, along with sites showing installation instructions; not that that any hand-holding is needed, since all you require is a little screwdriver.

I think you laid things out too well; perhaps they have nothing left to say? I especially liked the tin can needle scoop.

So, how did things go, Pigsticker?

Sealing and high-missive coatings for ceramic fibers and other surfaces Even rigidized ceramic fiber products still need to be sealed for safety. Furthermore, many of the coatings used for sealing provide a tough surface layer that holds high-emission coatings from peeling away from the fiber’s surface; an irritating problem that results from spreading some high-emission coatings directly on fiber blanket (especially when it is not rigidized first). Just as not all sealants are rated as high-emissive, not all high-emissive coatings are effective sealants, so you need to review the better-known products. There are also products, such as one shell coating for mold castings (consisting of zirconium silicate and fumed silica) which works quite well for surface sealing, and for heat reflection. I recommend this for those who don’t want to include a flame face layer of Kast-O-lite 30. ITC-100: This is strictly a high-emissive coating (not suitable for sealing); Twenty years ago, I found that deliberately separating it by adding more water to a small amount in a water glass, caused the non-colloidal particles to separate out, refining the coating, and greatly increasing its emission of radiant energy. My forge went from orange incandescence (when coated by the original product) to lemon-yellow, with just this change. I am not sure ITC 100 has the same ingredients today. You can make a more re-emissive formula, for less money than this product now costs. 100% colloidal zirconium flour can be purchased from various online sources, and mixed with phosphoric acid from your grocery store, to make a high-emissive coating, rated above (rather than “up to”) 90% “reflective” of radiant heat. Un-stabilized zirconium dioxide (ZrO2; AKA zirconia) has three phases: Monoclinic at less than 2138 °F (1170 °C), tetragonal between 2138 °F and 4298 °F (2370 °C). The transition between the first and second phase creates enough expansion to prevent it being used in hard refractory products, unless it is stabilized in the cubic form, or in its more useful partially stabilized tetragonal form. A small percent of calcium, yttrium, or magnesium oxides can be used to partially stabilize zirconia; cerium oxide can also be used, but is too expensive for this home-built equipment. Further high temperature manipulation can form fully stabilized zirconia, but adds further expense. Zirconia has very low thermal conductivity, yet very high luminosity when incandescent temperatures are reached. These two facts combine to make it a preeminent heat barrier. Because of the high luminosity, it can be used as an effective method of heat transference on high temperature casting crucibles, when applied in very thin coatings (.040” or less), and yet thicker coatings can be used to “reflect” heat through re-emission, while providing insulation that only improves as heat levels rise. When it comes to various heat barrier coatings, very fine particles of zirconium are desired, because the finer the particles the higher re-emission percentages go. Government sponsored experiments in the nineteen-sixties showed that phosphoric acid was able to hold stabilized zirconia onto heating surfaces despite phase change resizing; it was an important find—back then. But stabilized zirconia is much cheaper than it was in the past, and so this more expensive product is the better choice for tough heat barriers, and nowadays for some castable refractory crucibles. When used as a refractory; clumps of it are also used as insulation between crucibles and wire windings in induction furnaces. Zirconia based refractories, and alumina ceramics with stabilized zirconia included are well known for thermal shock resistance and resistance to erosion from incandescent liquid metals. Note: Drying can produce up to 4% shrinkage in slip cast zirconia refractories, and firing at 3452 °F (1900 °C) will produces up 15% further contraction; factors to be considered when planning structures made of it. Zirconia is available for use as grog, and is an effective loose insulation for very high heat environments (think of it as like Perlite on steroids). Zirconia also comes as stabilized ultra-high temperature porous insulating brick. Zirconium silicate: Many hobbyists concoct a tough sealant coating that is also a high-emissive product; they purchase zirconium silicate flour from a pottery supplies store, and mix it with bentonite clay powder; this is practical, because it does not go through phase shifts. Zirconium silicate, while very tough is only rated at about 70% heat reflection; it is also very resistant to borax, and an economical choice. Zirconium silicate can be either a coating or a hard refractory layer, depending on the amount of bentonite clay, etc. it is mixed with. One of the hobby blacksmiths on IFI makes a slurry of Zircopax (a brand of zirconium silicate) mixed into to colloidal silica (AKA fumed silica) and a little water; he also uses this mix for shell casting; he suggests mixing it to about the consistency of latex paint, in a clear lidded jar. The Zircopax will settle out, once you stop stirring every few minutes, and cake on the bottom of the jar, with the silica and water remaining in solution over it; until it is broken up with a butter knife, and thoroughly remixed back into solution. When combined with silica as a binder, I believe the overall performance of Zircopax in thicker layers will prove to be considerably higher than 70% heat reflective, since the other part of its molecular structure is clear natural silicate, which will pass light rays with very little interference, and since its re-emissive mechanism is radiance, I believe its overall performance in thicker layers will prove to be much higher than it is rated for. Remember that each layer must be fired before the next layer is painted on. Tony Hansen, of Digital Fire fame, uses Zircopax as both a coating and a solid refractory, very like clay, but good to very high temperatures, and highly insulating; two qualities that mere clay lacks. Mr. Hansen mixes it with Veegum T (a smectite clay) as a binder and plasticizer. A mixture of 97% Zircopax and 3% Veegum can be molded into structures, as easily as potters clay. A mixture of 95% Zircopax and 5% Veegum provides a hard tough heat reflective coating for other refractory structures. Mr. Hansen has also created his own 5mm thick (just over 3/16”) kiln shelf, which he states “will perform at any temperature that my test kiln can do, and far in excess of that.” It consists of 80% Zircopax Plus, with 16.5% #60 to #80 grit Molochite grog, and 3.5% Veegum T; he states that the mixture is plastic and easy to roll out, with 4.2% shrinkage, with 15.3% water added, but suggests that you dry your forms between sheets of plasterboard, to prevent warping. Firing to cone 4 produced 1% shrinkage, and left his shelf only cinder bonded. Firing to yellow heat will produce further shrinkage, but strengthen the final product; this has about the same thermal shock resistance as high-alumina cast refractories. Avoid uneven heating by setting your forge or kiln up to work as a radiant oven. Read about Zircopax at: https://digitalfire.com/material/zircopax Read about Veegum at: https://digitalfire.com/material/1672 Plistix 900 F: Plistix is a 94% corundum aggregate and matrix, with a phosphate bond; it can be either a coating or cast refractory, depending on the amount of water used; it is use rated to 3400 °F. This product can also be used as a firebrick mortar. Matrikote 90 AC Ceramic Coating (one of the product line from Allied Minerals) is a very tough hard fine grained high alumina refractory coating containing 90.4% alumina, 1.5 silicon dioxide as a vitreous(glass-like) binder, and 2.7 % phosphorus oxide as a polymerizing binder. Matrikote is good to 3000 °F, and would prove useful as an inner layer between outer coatings of higher use temperatures and rigidized ceramic fiber products. Satanite is probably the best-known refractory mortar that is also used as a hard coating/sealant over ceramic fiber board; it is use rated at 3200 °F, and is easily purchased in small quantities through knife making suppliers. But refractory mortars are not recommended as flame faces, so plan on using a different finish coating on interior surfaces; It is excellent on exterior surfaces. Sodium silicate is a white powder that dissolves in water; it is usually sold in bottles, with the water already added; it is commonly used to glue the little bits of Perlite together into a solid layer of secondary refractory insulation, as both products melt at about 1900 °F. Sodium silicate is also used to glue refractory fiber products unto other surfaces, like the inside of forge shells (containers). However, when used this way, ceramic blanket should be rigidized completely through all layers, to keep it from de-laminating, and falling away from the glued surface over time. So, why use it at all then? Sodium silicate hardens through contact in the carbon dioxide in air; it doesn’t need firing to work; fumed silica must be fired. What are you doing awake this early in the morning? I just can't sleep all night; been up since three.

BTW, those where all very good points, AFB

The British thermal unit (Btu) is a well-known unit of potential energy, which has long been used to compare fuels, and burner heating potentials; it is less legitimate for judging burner types. On top of this, you very rarely see it tied to burner turn down ranges, leaving us to ask questions like 140,000 Btu at what gas pressure; so far over a reasonable top pressure that that the burner's flame had long since started running rich? The problem is that actual heating potential is a slippery fish, even in a saint’s hands, let alone an ad manager’s. Even if you do all the figuring for yourself, what does 140,000 Btu actually mean to YOU; at best it gives you a general impression of what a burner should be able to do; and that’s where you were when you came in! For instance, if two different burners are running the same gas pressure from the same gas orifice diameter, but one only puts out 2400 F flames, but the other one puts out 2800 F flames, their BTU consumption matches, but nothing else well.

Sealing and high-emissive coatings for ceramic fibers and other surfaces Rigidized ceramic fiber products still need to be sealed for safety. Furthermore the various coatings used for sealing tend to create a tough surface layer that holds high-emissive coatings from peeling away from the fiber’s surface; an irritating tendency that results from spreading high-emissive coatings directly on fiber products (especially those that aren’t even rigidized). Just as not all sealants are rated as high-emissive, not all high-emissive coating are sealants, so we need to review the better known products: ITC-100 is strictly a high-emissive coating; I have found that deliberately separating it by adding more water to small amounts in a water glass, causes the non-colloidal particles to separate out, refining the coating, and greatly increasing its emission of radiant energy. For less money than this product now costs, 100% colloidal zirconium can be purchased from various lab suppliers, and mixed with phosphoric acid from your groceries store, to make a high-emissive coating rated above 90% “reflective” of radiant heat. Frosty and others on this group concoct a tough sealant coating that is also a high-emissive product; you get the zirconium silicate flour for it from Seattle Pottery Supply (or other pottery suppliers), and mix it down with clay powder; ask them for particulars. Zirconium silicate, while very tough is only rated at about 70% “heat reflective,” but I think this figure is misleading; since the other part of its structure is clear natural crystal, which will pass light rays with very little interference, and since the actual mechanism for its “heat reflection” is re-radiance, I believe its overall performance in thicker layers will prove to be considerably higher than 70%; it is also very resistant to borax, and an economical choice. Plistix 900 has 70% heat reflection, and makes a tough smooth sealing coat rated for use at 3400°F. Matrikote 90 AC Ceramic Coating (one of the product line from Allied Minerals) is a very tough hard coating containing 90.4% alumina, 1.5 silicon dioxide as a vitreous(glass-like) binder, and 2.7 % phosphorus oxide as a polymerizing binder. Matrikote is good to 3000°F, and would prove especially useful as an inner layer between outer coatings of higher use temperatures and rigidized ceramic fiber products. There are other bonding mortars and high temp coatings. Probably the best known refractory mortar for use for hard coating ceramic fiber blanket is Satanite; it is use rated at 3200 F, and easily purchased in small quantities through knife making suppliers on the Net.

One of the things I noticed about tungsten carbide rotary files, is that the larger their diameters are the further they fling those needles. Over time, I came to stick with 1/8" diameter files, whenever possible.

Caution: Tungsten carbide rotary files fling tiny needle-sharp slivers. You need to wear goggles, or at least glasses, for eye protection. You are also advised to wear long rubber dish-washing gloves, or a rain coat with latex gloves, to keep them out of your skin and clothing. Immediately after use, remove and shake out dish-washing gloves and rain coat. Discard latex gloves. Sweep away the slivers from parts and equipment surfaces, with a brush.

It will give you all of that. More to the point, it will awaken your appetite for gas forging; this is why you want to hold on to the other forge parts. Yet, no matter what other forges you buy or build, that first small forge will remain you preferred tool, because it costs the least to run, and doesn't over heat your shop in "the good old summer time."