Forges 101

[Another FrankenBurner]

I have a couple of those cheapo regulator hose combos. I also have a good regulator bought many years which was more expensive than the two.

The cheap ones aren’t smooth. I have to fiddle with them sometimes. A small knock to the side after adjustment.  Turn the tank off, back the regulator out, tank back on, slowly adjust. That kind of thing.

 Better than not having one though.

[Mikey98118]

'Bargain' regulators and needle valves always look like a good idea, when someone is buying all the supplies needed to build that first forge; they never are, when they have to be replaced...or lived with

[Mikey98118]

 

After years of watching others aim their flames toward the far side of the floor, from burners positioned at at ten or two oclock, I am persuaded that it is the better choice.

[Mikey98118]

 

                           What does a hot efficient forge take?

(1) Good design; this starts with size. Make the forge no larger than your present needs--not as large as you suppose you could need, eventually. Shape is also a concern. Your forge should be no longer than one and a half times its width, and about two thirds as high as its width; these proportions apply to tunnel, "D", oval, and box forges. The best shape for a first forge is variable (brick pile forges). Burners should have sliding air chokes on their mixing tubes, so that the amount of secondary incoming air, which the burner's flame is inducing, can be controlled. The speed of exhaust gases exiting the forge should be controlled with a baffle wall, while radiant energy is reflected back into the forge.

(2) A hot and efficient burner; while this is certainly an important part of any forge, you will note that it is secondary to good forge design. A miserable burner cannot properly heat the best gas forge; but a merely average burner can do so.

How is this possible? A proper gas forge becomes a radiant oven, once heated. Any carbon monoxide  gas (secondary flame) Is quickly consumed within the forge, so that only hot exhaust gases escape the forge--not flame.

[Mikey98118]

   

                                                                  Why 1/4" and 3/8" burners?

The only equivalent commercial source to small burners are standard dual-fuel torch-heads, which will last fast as a hand torch being run on  MAP fuel (polypropylene), and even faster mounted in heating equipment, even when only run on propane; the problem in both instances is their paper-thin flame retention nozzles. At high heat levels, which are obtained with  (polypropylene) burning in the open air, and with propane burning in a forge or casting furnace, even a stainless steel flame retention nozzle will oxidize away over time; the thinner the nozzle the less time that takes. Flame retention nozzles must be considered as a consumable item; the thicker they are the better. The thin none-replaceable nozzles on commercial dual-fuel torch-heads are simply a rip-off.

    So, using a dual-fuel torch head in your two-brick or coffee-can forge isn't going to be the cheap and easy path, unless you think replacing them, instead of just a flame retention nozzle is going to save time and money!

  An even worse choice, is using one of the older propane torch-heads, with a brass flame retention nozzle, laid in an over-size burner opening (to keep it from melting); this saveS the torch will wasting lots of expensive fuel.

 

[Mikey98118]

It should be about time for people to ask some questions, to help them finish their garage and barn warmers...er, I mean forges, before icicles start forming on the eves

[Mikey98118]

“Just buy a Dremel” can be sound advice when it comes to some of their rotary tool accessories, and attachments. If you do not want to pay close attention before every purchase; if you would rather “just get on with the job,” then paying their top prices for consistent (not necessarily best) quality is a practical choice. As you get comfortable using rotary tools, you will inevitably modify that choice a lot. With sixty-five years “on the tools,” I still choose to pay Dremel prices at times; but never out of brand loyalty.

    I think that the Dremel 575 Right Angle Attachment, 4486 Keyless Chuck, and A550 Shield are worth their prices, and will greatly aid you to do build your forge. The EZ Lock mandrel and abrasive cutoff discs are worth every penny; so are Dremel’s 420 cutoff discs; their model #100 and #200 rotary tools are worth their cost. But, paying Dremel prices for their other stuff? Not these days.

[Mikey98118]

 

Miniature adjustable three-jaw rotary chucks: A keyed chuck needs to have reasonable quality to successfully spin an accessory, or drill bit, at high speed. So, what about key-less chucks (finger & thumb tightened) for rotary tools, sold online and through jeweler’s supply stores; the kind that has three independent moving jaws? I bought three of these cheap imports, before giving up; they all froze, and broke during their first attempted use. Why? It turns out that none of them were a Dremel 4486 Keyless Chuck. Dremel has their brand name to protect; anonymous drop shippers do not. Make sure that you are purchasing your “Dremel” chuck from Dremel. What is clever about this chuck is that they designed it to thread directly unto a standard rotary tool’s 9/32-40 threaded spindle, greatly increasing its stability, by making an end run around the weak spot in most rotary tool chucks—their skinny shanks.

    While better than no-name chucks, it is still not anywhere near as good as a miniature keyed chuck (used on DC motors to make micro-drills). However miniature keyed chucks often suffer from the poorly machined brass arbors that come with them. It is better to buy a steel JT0 arbor for them, to avoid run-out problems.

An inexpensive keyed chuck and steel JTO arbor, that is made for use on DC motors, is sold by Walmart.

Foredom A-MC2 Micro Chuck:  Foredom makes a rotary tool chuck from high-speed steel, which is just okay; it is a jeweler type, which employs an integral castellated collet that squeezes all four jaws closed as a single unit, to create a type of variable diameter  collet chuck; it still isn’t as smooth as a set of brass drill bit collets. Why not? It is machined to about 0.001" (one thousandths of an inch) tolerance, and extends well beyond the spindle’s end. Really smooth performance in this instance would probably require 0.0002" (two ten-thousandths of an inch) tolerances; producing that level of quality would price it out of the market. What this chuck does do well is act as a protrusion, to help extend the reach of grind stones and drum sanders deeper into small tubes (which need to be increased a few thousandths of an inch in diameter for fit-up). Remember to dress any stone, or rotate any drum you spin in it (to offset run-out), before inserting it into the work piece.

    Accessories with 1/8” shafts are cheap and easy to find; this variable chuck is also used to accept micro drill bits, which have varied shaft diameters. Google “adapter chuck for drill bits” or Foredom® A-MC2 Micro Chuck to see what is currently available. Do be sure to read customer feedback about any chuck you find tempting; good designs don’t count for much, without sufficient quality control.

[Mikey98118]

Alternatives to high-speed steel drill bits: Why do those drill bits in your rotary tool accessories kit, always prove worthless? High speed steel drill bits, which lose their temper (hardness) at around 420 °F, have been used in rotary tools to drill wood, aluminum, brass, and plastic for decades. Mild steel, and especially stainless-steel alloys, are more easily drilled with cobalt drill bits, which are high speed steel with cobalt added (hold’s temper to 1100 °F), starting with M-35 (5% cobalt); the next higher grade is M-42 (8% cobalt); both grades have reasonable prices online, but not at hardware stores. M-42 has superior wear resistance. If M-35 is all you find offered, jump on them with a big toothy grin. While M42 is harder than M35, it is also more brittle.

    Sets of micro drill bits are usually made from tungsten steel (high-speed steel with tungsten added); these will hold their temper up to 932 °F. Tungsten steel is also tougher than plain high-speed steel; both important factors when drilling in stainless steel. Some sets of micro drill bits are tungsten carbide, which will take much more heat, but is also more inclined to break due to its increased brittleness.

    So, the point of tungsten steel, and cobalt steel drill bits in your rotary tool is less about their increased toughness, than how much heat they can withstand, while being spun at much higher speeds than is recommended for their size, when drilling steel.

 

[Mikey98118]

Properly securing and balancing rotary accessories: Fully insert accessories into the tool’s spindle, and just snug the collet nut; do not over tighten, or you might strip its threads, or worse, the spindle threads. There is a good reason why collet wrenches are so tiny. Take the hint.

    I have yet to buy an accessories kit that does not include a little rectangular silicon carbide dressing stone; they are used to help balance the softer aluminum oxide grinding stones, wheels, and cut-off discs. Employ that dressing stone to counter-balance accessories; keeping your rotary tool from suffering degradation from excessive vibration. Cheap rotary tools are likely to have spindles, which were machined significantly out of true with the tool’s axis; if you add unbalanced accessories to that, bent shanks and thrown accessories are the next trouble that will be flung your way. A few light touches, with a dressing stone, can save you a lot of grief. You can also buy inexpensive, larger, dressing stones, when it wears out.

    Rotate accessories that can’t be balanced with a dressing stone (like steel discs, brushes, and sanding drums) a quarter turn at a time (in the spindle), to improve balance.

Accessory shank and collet diameters need to be properly matched. Some accessories being sold as 1/8” actually have 3/32” shanks (common with engraving, and nail grooming accessories that were designed for pencil rotary tools). An eighth of an inch is 0.125”; also 3.2mm (which commonly turns out to be only 3.17mm).

    But, 3/32” shanks are more than 0.031” smaller than 1/8”; they will end up loose enough to vibrate their way out of a 1/8” collet. What to do? Buy a cheap set of brass collets; there will be a 3/32” collet among them. 3/32” shank accessories were designed for use in pencil rotary tools; their weak motors slow down the minute the accessory starts being worked; thus, the weaker shank is no problem, but that that may not hold true in a 160-watt rotary tool. You should reduce speed a little, when using them.

3mm shank accessories: When you see an ad for 1/8” (which is 3.2mm) accessories, followed by a description change to 3mm, you can depend on them being only 0.118” diameter shanks; not 0.125”; this may not stay gripped by your tool’s 1/8” collet, but is too large to slip into a 3/32” collet. Millimeter collets are sometimes available, but it is simpler to employ a Dremel keyless rotary tool chuck, or a keyed chuck in a micro-drill to use 3mm shanks safely.   

 

Extended-shank accessories: Fully inserting extended-shank tungsten carbide rotary burrs isn’t sufficient to keep them from bending. You must also run 4” long rotary shanks (1/8” diameter) at half speed, or less. Also run 4” long die grinder (1/4” diameter) shanks at half speed or less. 6” long shanks should simply be avoided, or cut to 4” lengths). If extended shank burrs are spun too fast—or are cheap versions of legitimate burrs—they will certainly bend in seconds. Why are accessories made with “overlong” shanks in the first place? So that they can reach further into internal areas (as in pipes and tubes); they were manufactured as specialty accessories. Since speed must be reduced according to shank length, consider cutting extended shanks down to just what is needed to get a particular job done, and no longer, because the longer the shank the more the tool must be slowed.

Freeing up jammed accessories: Collet nuts on rotary tools may need to be sharply rapped once or twice with the tool’s tiny wrench, to free up jammed accessories. Unscrew the nut a partial turn, so that the accessory can slide free; sometimes, they will revolve, but cannot be slid forward and removed. What has happened is that the collet, which the accessory’s shank slides into has jammed in place, locking the accessory’s shank together with the collet. Tap sharply, on the end of the nut with nothing larger than the tiny wrench that comes with your rotary tool; this will transmit just enough of a shock wave through the parts, to break the collet’s grip.

    Should a new tool come from the factory with the collet stuck in place, unscrew the nut a couple of turns, and poke the shank of an accessory against the top of the collet (at an angle), to break it loose.

    If you change accessories frequently, you may find relief from sticking collets with a brass collet nut; brass collet kits, which include 1/8” collets, sell for around $7.00 on eBay and Amazon.com. Just as some collets release better than others, some collet nuts are better too. Most collet nuts fit other spindles, so switching a better collet nut from a less used rotary tool to your favorite, should be an obvious move.

    Many people simply replace the collet nut (and its sticking collet) with a Dremel keyless chuck. Make sure to buy this attachment from Dremel; a cheap look alike won’t work very long, if it even works at all. How clever is this move? Enough that a few rotary tools are now being sold with this kind of chuck, instead of a collet and nut. Nothing succeeds like success.

    That said, even the Dremel chucks are not problem free. Keyless chucks cannot be tightened anywhere near as effectively as keyed chucks, or even collet chucks, and these tiny keyless chucks increase that problem; obviously, your whole hand can tighten a keyless chuck on a drill motor far better, than a finger and thumb can tighten one of these. Some people have ended up using pliers. A drop of oil or lithium grease in one of the jaw ways (the groove they ride in) will smooth performance.

Run-out (AKA runout):  Any rotating tool is meant to revolve on its center. If its spindle isn’t machined true (centered and parallel to its axis), accessories mounted in a rotary tool, or die grinder will orbit in a tiny circle around its axis, instead of revolving on it, producing heavy vibration; this is called run-out. In fact, it is inevitable that all rotating tools will have some run-out; just not a noticeable amount.

    If a micro drill’s keyed chuck is not mounted true on the motor’s spindle (usually because the tiny brass arbor that connects them is not machined true, or carefully mounted), the micro drill bits mounted in the tool will also orbit around a tiny circle, and quickly break. Any drill bit, or stone mounted in the tool will have the same problems as they do in rotary tools and die grinders with run-out, but to a lesser extent, because of the drill’s lower speed range.

    The larger an abrasive stone’s diameter the easier it is to break; especially in a tool with run-out. If you cannot deal with that, there are tungsten carbide burrs that won’t break anywhere near as easily; of course, a tool that is heavily vibrating from a run-out problem will tend to fling them about. But at least this will adequately demonstrate that the stones were never your problem. Diamond coated chainsaw burrs, don’t break apart; nor are they as inclined to be flung about, as tungsten carbide burrs. But, run-out will quickly dull the diamonds, and even knock patches of the diamond coating off.

Abrasive stones versus wheels: Stones have advantages for working inside small tubes and pipes. Wheels grind faster than most stones, because their larger diameters create higher surface speeds, if the pipe or tube is large enough for their use; of course, a dressing stone can always make the wheel fit. All of these products consist of abrasive grit bonded together by resin. But stones are also glued onto their steel shanks, creating a separate failure point. Wheels have arbor holes that accept steel mandrels, so wheels are simply more durable than stones.

    Most wheels are ¾” to 7/8” diameters, with 3/32” or 1/8” arbor holes and 1/8” thickness; they can be used to finish grind small air openings; when they dwindle down to smaller diameters, they can be used to flatten internal weld beads and enlarge short areas of pipe and tubing for fit up.

[Mikey98118]

Mounting a homemade side handle: Rotary tools and die grinders can be braced for straight travel (like surface cutting with angle grinders), rather than the typical swinging arm motion (tendency to curve, binding the disc, resulting in kickback), by mounting a side handle near to the tool’s spindle; this provides greatly improved control. Twenty years ago, 2” angle grinders like Proxxon’s Long Neck Angle Grinder, or the Merlin 2 from King Arthur Tools, were the only electric tools that could easily make straight line cuts in small burner parts; they were designed for inline motion, and had steel safety guards. A rotary tool with a safety handle mounted can now do a better job, more safely, for a small fraction of their prices.

    What has changed, to make this possible? See-through safety guards couldn’t be purchased back then; they can be now. When cutting along an ink or scribe line, it is tempting to bend over the tool, to provide an adequate view; a very bad habit, unless the tool has a safety guard; it’s also frustrating to try to see the cut line by peering around steel guards. But you can place your disc right beside the cut line, and work in safety and comfort, when you see the line by looking through the guard.

    Some rotary tools already have a removable plastic handle, but they are set up at about seventy-degrees for increased comfort during buffing, grinding, and drilling work; not at right angles, for better control during a surface cut.

    Most hand-held rotary tools have a threaded plastic neck area around the base of the spindle. This threaded neck is 17mm diameter protruding from the plastic housing’s shoulder; this is the area that a sheet metal side handle can set in, trapped between a plastic shield, or just the original plastic threaded colloar, and the tool housing’s shoulder. Dremel popularized those same threads to securely mount attachments, such as their flexible drive shaft. Then, other manufacturers copied Dremel. The threads on safety shields are 17mm (0.670”). It is easy to buy a 3/4” flat washer. A flattened tube end can be welded, or brazed to the washer, creating a similar kind of handle as the ones that provide ergonomic stability to angle grinders.

    Or, you can layout a washer and handle shape on a piece of sheet metal, and employ your rotary tool to fashion a side handle; this allows the use of aluminum, stainless-steel, or brass sheet metal, which will never rust or need painting. A plastic rotary shield, or original threaded collar, securely traps it in place, when needed; or it can be quickly removed, when it would be in the way (during drilling, and some grinding tasks). It should prove very helpful during beveling with tungsten carbide rotary files.

    Why bother? Because a swinging wrist movement can’t be braced anywhere near as effectively as inline movement (which only becomes practical with the aid of this side handle). Where the handle is positioned has nothing to do with whether you are right or left-handed, and everything to do with moving the cut-off disc opposite to the direction that the disc is trying to force the tool to travel along part surfaces. You need the handle to help tow—never push—a cutoff disc forward along the cut line, once it starts to break through the kerf.

    A side handle helps the disc to grind a straight line through the material from the formation of a groove through to the end of the cut, greatly reducing kickbacks; especially when dealing with the last fraction of an inch at the end of a line.

    Best procedure is to run the disc back and forth on the part’s surface, while a groove forms and gradually deepens, cutting through the part only at the very end of the process; this means that increased control of your arm movement, becomes more essential—not less.

Warning: The main point of a side handle is to help in surface cutting with cutoff discs, or  when beveling with a tungsten carbide rotary file. But cutting and beveling with an electric die grinder must be done much more carefully, than with a rotary tool.

(1)       Cutting safety also requires a power switch with the right location and type. The switch must be easy to shut off, without jiggling the tool, in the slightest degree. Movement while turning the tool on doesn’t matter, since that is always to be done before touching the work.

 

(2)       A full-power die grinder (400 to 550 watts) must be run at half speed during surface cuts. A medium-power die grinder (220 to 280 watts) can be run at full speed.

 

(3)       The cutoff disc should not be larger than 1-1/2” diameter; smaller is safer. Take your time working up to the fastest speed, and largest disk, that you personally can safely use.

 

(4)       The disc must be breakable; a resin-based friction disc; and thinner is safer than thicker; it is not less likely to break of course, but will be that much less likely to fling the grinder about while doing so. Do not employ a grit coated steel disc, or a toothed circular saw blade, even in a medium-power electric die grinder. When kickback occurs, it is necessary that the accessory be destroyed, rather than the grinder being savagely flung about near your body. Do not kid yourself that you will always avoid kickback; that is not in the cards.

 

(5)       A die grinder should not be used for surface cutting in confined spaces, or with your body unable to be properly braced, with or without a handle installed. If you must cut in a confined space, use a 15/16” friction disc, on a rotary tool (nothing with more torque); better safe than sorry.

 

Safety, is seldom an absolute, except in the negative sense. “don’t ever do that” is clear and simple advice. To suggest that someone “do that safely,” is absurd. Whenever you attempt to do anything, some risk is involved. Using an electric die grinder, can never be perfectly safe; cutting with one can involve substantial risk; especially if safety procedures are not observed.

    Why not use one of the new mini-saws, instead; isn’t that what they’re for? If you are cutting on flat surfaces, yes. If you are cutting off the ends of angles or pipes, the saw still maintains an advantage, so long as you pay close attention. When cutting into pipe or tubing, no. If you are cutting into curved surfaces on cylinder ends, to create equipment shells, no.

    When grinding, sanding, or wire brushing with a die grinder, there are safer choices too. A brush shape is generally safer than a cup shape, which is usually safer than a wire wheel, because with every change of shape the accessory’s diameter tends to increase. A diamond coated burr is the least likely accessory to generate kickback, followed by a stone burr. Solid tungsten carbide burrs are most likely to create kickback; of these, double cut burrs will create stronger kickback than single cut burrs (of the kind meant for steel work; not the large grooved burs used on aluminum, brass, and wood. And of course, the larger a brush, burr, stone, or sanding drum’s diameter the harder any kickback will be. The stronger the tool’s torque the harder its kickback. The higher the RPM the harder the kickback.

[Mikey98118]

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.

[Another FrankenBurner]

Don’t forget to check your boots. These little slivers come off my boots right where carpet begins in the house to be found later with bare feet.

Also don’t forget to wipe your hair and even eyebrows after using a burr. It’s frustrating to wear all your safety gear only to have something sharp fall into your eyes when you are taking the gear off.

[Mikey98118]

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.

[Mikey98118]

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.  

 

[Mikey98118]

22 hours ago, Another FrankenBurner said:

Don’t forget to check your boots. These little slivers come off my boots right where carpet begins in the house to be found later with bare feet.

Also don’t forget to wipe your hair and even eyebrows after using a burr. It’s frustrating to wear all your safety gear only to have something sharp fall into your eyes when you are taking the gear off.

BTW, those where all very good points, AFB

[Another FrankenBurner]

They are good points. Really sharp and they manage to go everywhere. 

I like burrs when I need one. When I’m done I have a full routine of shaking my clothes and sweeping the area before doing anything else.

I also don’t mess around when it comes to PPE here. Safety squints are not acceptable to me with burrs. Either goggles with gasket and/or a face shield.

[Mikey98118]

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.

8 minutes ago, Another FrankenBurner said:

They are good points. Really sharp and they manage to go everywhere. 

What are you doing awake this early in the morning? I just can't sleep all night; been up since three.

[Another FrankenBurner]

I’m an early riser.

Three AM is no fun though. I do that too. My mind always churning.  I started taking magnesium glycinate supplements which seems to help a little.

[Frosty]

Years of needing to make a 6:30 dispatch set my sleep rhythm to a 3:am wake up, sleeping till 5 leaves me loggy for a couple hours till I wake up fully. 

I use a welding magnet in a plastic bag and a steel "tin" can I slit into a scoop to catch the majority of steel slivers when I use rotary burs. It's not 100% but catches most of the little devil spikes. I wear bug eye goggles over my trifocals under my face shield. A welding skull cap type hat, bill backwards over my collar. I go over myself with a clean welding magnet in a plastic bag before taking my goggles off. I have really good luck wearing my Helly Hansen rain gear and Extra Tuffs. They're pretty proof against the little needles and I can hose myself off before taking them off.

I've wanted to make a dust comp with my shop vac but it makes me antsy sucking even potential sparks into a shop vac. 

What say everybody, how do you deal with invasive grinding debris like the little devil needles a rotary burr produces?

Frosty The Lucky.

[Mikey98118]

On 12/1/2023 at 8:10 AM, Frosty said:

What say everybody, how do you deal with invasive grinding debris like the little devil needles a rotary burr produces?

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

[Scott NC]

  If possible, enclosing your workpiece can help.  A big cardboard box, an improvised canvas tarp "tent", whatever works to contain them.  I have often wondered if a neodymium magnet fixture of some configuration would grab them.  Have fun cleaning that off.

[Mod34]

MOD NOTE:

Mikey98118's most recent comment on speed controls has been split into its own thread:

 

[Mikey98118]

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.

[Mikey98118]

 

On 12/11/2023 at 6:25 PM, Mikey98118 said:

    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.

    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.