Mikey98118

Ramp the temperature up slowly, to begin with. Give time for whatever steam forms, to escape, rather than build up pressure. Just bring it up to red heat two or three times, before "going for it." I think you will be pleased with how well it works.

Isn't it great what some vibration does to smooth out a refractory casting

Thanks, Frosty. Any more of you people out there, willing to share?

One millimeter spheres should be okay. Perlite is fine, but you will probably want to finish coat the flame face with Plistix, to smooth its surface. Remember that a smooth surface radiates heat back into the equipment interior far better than a rough surface can; that is the genius of Plistix.

I remember back before the home our casting groups "discovered" Kast-O-30; they were using chicken wire in the hope that it would help keep our refractory together a little longer, after it started cracking. In those days, we all mixed Perlite into the refractory mix, to make insulating voids. So, the insulating, and lightening aspects of Kast-O-30 were no big deal to us, but its fracture resistance made it an instant hit Egad! That should read "our home casting groups" and "Kast-O-lite 30"...

I love hearing the private methods guys have come up with to do their work; spent decades dreaming up my own

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.