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Kang

Kang's Kreations - Molten Metal Madness

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Oh, I just realized I forgot to include a pic of the plinth I made for my crucibles to sit on. I had some extra refractory mixed up when I was done pouring the hot face of the furnace earlier, so I grabbed my recip-saw vibration tool and an old margarine container and went to town with what I still had mixed up. As it happened, I got lucky. There was just enough to make a plinth that was just the right height and width I would need - tops of plinths should be the same width as the bottom of the crucible, and they should be just tall enough that the top of the plinth AKA bottom of the crucible is right at the same height as the midpoint of the burner. Somehow I nailed that without even thinking too much about it - I guessed that the marg. container might be close to the right size, and I was pretty sure it would work in a pinch, but it turned out pretty much perfect, woohoo!

 

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Now onto the final part of the build...

 

 

Building Balerion, the Black Dread: Step 7

 

Lighting a fire!

 

 

With the entire furnace built, all that was left was to fire the refractory lining. I left it sitting in my shed with a 100W incandescent bulb shining into the interior for a month or so, to use the bulb's warmth to help slow-dry the refractory while I waited for a weekend day when it wasn't raining when I'd have basically the whole day free for firing the refractory - that is not the sort of thing you can start up and just walk away from. Surprising how warm the inside of the furnace got!

 

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(I actually had the whole lamp hanging inside the furnace by its cord for most of that time, this is just the best pic I could find as an example. This might actually be from before I cast the hot face - see the lack of black paint...)

 

Finally the big day came. It was past time to light a really hot fire! I started out running my burner on propane. It is a waste oil burner, but there are two types of oil burners typically used in a backyard foundry - simple dripper burners like mine that require a preheated furnace to vaporize and ignite a series of oil drips that are being blown into the furnace, and complex atomizing nozzle burners that use compressed air or an oil pump to siphon or push oil through an atomizing nozzle ready to ignite without preheat. Since mine is a dripper, I dont't need any fancy nozzles that can clog on waste oil or an air compressor, but I do need to preheat. It has a propane line plumbed into it for that. It needs to run on propane until things inside the furnace are glowing red hot, ie. hot enough to vaporize the oil drips. I kept it as low as I could, watching for steam coming off the refractory. When I saw steam, I waited for it to dissipate before turning up the burner just a little, at least in theory. Once it seemed to be hot enough to keep the furnace lit, I mostly closed the lid. Mostly but not quite - I propped it up maybe a cm or so above the furnace wall to allow the heat to get between them and cure the sections that are normally sealed off when the lid is closed. Although I did open it up for many of the pictures I took from this point on.

 

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Once the furnace had been slowly brought up to a high enough temperature, I started the oil drip. To many it probably sounds as if burning used oil would be really smoky. Not so, if you also add enough air to allow the oil to combust completely. With a closed furnace, it is pretty easy to adjust things close to a neutral mixture by eyeball (as opposed to a rich AKA reducing mix which means there is more fuel than can be burned with the oxygen present, or an oxidizing AKA lean mix which means there is more air than needed). A neutral burn means no smoke; smoke is really fuel that escapes from fires that don't have enough air to burn it. That would be a rich mixture. A rich burn can cause gases like hydrogen (from the hydrocarbon fuel - not as big an issue using charcoal) to dissolve into the molten metal; when it freezes, the hydrogen comes out of solution and you end up with tiny bubbles - porosity in your casting - which may not show up until you cut through it to remove the gating or need to do any machining. This is fine for ornamental work, but not great when you are trying to make something functional like engine/machine parts, which is why many foundry hobbyists get into this game (not me, I am just addicted to molten metal). A lean burn creates oxidizing conditions inside the furnace which can cause holes to get burned into crucibles and eat away at refractories as well as turning more of the melt into dross than is necessary. When melting aluminum, we shoot for a slightly oxidizing burn - it is easier to skim off a bit of dross before pouring than it is to remove hydrogen gas from it (although that is possible and kind of fun).

 

I was trying to bring the furnace slowly up to a pretty much white heat. So the way I slowly turned it up was as follows: I would open up the needle valve controlling the drip rate of the oil, and watch the vent in the furnace lid. Fire and some smoke would come up through the vent - a sign of richness. Soot building up in the vent hole is another; all the fire inside the furnace and the soot burning away indicates you've crossed back to the other side of neutral into oxidizing territory. So I would turn up the blower a little bit, watching the flames pull back inside the furnace, or perhaps licking up out the vent an inch or two at most. Then I would let it sit a bit and open up the needle valve a little more. Lather, rinse, repeat, until the blower was running full tilt. I was also backing off the propane a bit each time I turned up the oil. Before long, it was runing on pure oil. Well, actually I used diesel. The burner will run on any liquid that will burn once vaporized - diesel, kerosene, waste vegetable oil (WVO), waste motor oil (WMO), perhaps alcohol... Gasoline not so much, that stuff is too volatile. I want a fire, not an explosion! Diesel was an easy choice because I did not yet have a supply of waste oil, and it is also a little easier to run through a burner because it flows like water.

 

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(At this point I removed my poor old steel crucible, which was never meant to withstand the blast of an oil burner, especially for any longer than it takes to melt a pot of aluminum - it was only in there to give the flames something to swirl around while the furnace got hot anyhow)

 

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Once I had it running full blast, I kept it going for a while until I was sure the refractory hot face was glowing that hot all the way through its 1" thickness, fully fired and ready to use!

 

- pix with burner having been shut off:

 

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Tuyere cam!

 

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Underside of the lid:

 

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Hard to get an accurate pic of glowing hot things, that camera sometimes dims the whole image to compensate. This furnace should serve me well for many years to come. It's been almost a year already, though I must admit I have only done 3 casting sessions with it since completing the construction - the 'first pour' video above was one (my first and only 2-melt casting session to date, note, the second melt went really fast because the furnace was still hot from the first), followed by casting King Robert's Rammer, and then of course the bronze axe, my first ever bronze melt. But not my first melt of copper alloys - remember that brass tube stuck in the drain hole? that ended up being my firt ever brass melt - it finally came out during the firing of the refractory... :)

 

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Not a lot of castings cranked out this year, but that is because I was focusing on getting my sand casting system up and running. Lost foam is fun and an easy way to jump into metal casting because you don't need a lot of tools and equipment other than a way to melt and pour metal - other than that it's just carved styrofoam and hot glue and loose dry sand basically straight out of the bag from the big orange box. But unless you are able to make your own styrofoam patterns by steaming EPS beads in permanent steel molds and own a sand-fluidizing vat for burying them in and have access to expensive investment mixtures (not financial, I'm talking about plaster-based or ceramic shells used to coat the foam that like the big boys in Big Automotive use (which would negate the benefits of lost foam for the beginner completely), it's a lot of carving for an uncertain result and a lesser finish needing more sanding and grinding to get all shined up later. Sand casting patterns can be resued many times and the molding sand leaves a finer finsih. Gotta say, bulding Big Bucket Mull took up more of my summer than I'd hoped it would. But it was necessary to keep my greensand in usable condition. I'm old enough now to say nope, I am just not going to be mulling even my small 100lb supply by hand; it's too hard on the hands and the knees IMO, but it is technically possible. It just takes hours longer and isn't as effective, is all.

 

That's about it, nothing left in step 7 but some pictures I took the next morning once everything had a chance to cool down. The refractory got really white when it was fired; I thought it looked dry before, but it was a bit grey compared to post-firing. I guess some of that is chemical reactions, but some of it is from drying completely.

 

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Not too many cracks, although some did appear in the bottom of the drainage channels leading to the drain. There was also one hairline crack in the wall. This is normal, and to some extent it is good because it relieves some of the internal stresses in the wall as it heats up from the inside out. Not a big concern, just something to keep an eye on and maybe patch up some day if they start to spread. Lid seems to have held up just fine for now... Hopefully it will stay strong; lids are the failure point for a lot of homemade furnaces... I have enough leftovers to build another if need be.

 

One thing I did not mention above is that I had some trouble running my burner on propane. Once I got it lit, it would stay lit if I left it alone, but whenever I tried to turn it up a little, it would go out. As a result I ended up not ramping up the heat as slowly as I would have liked to, but it worked out OK anyhow. This stuff is professional grade and a hobby foundry is obviously much less harsh than a full production business. Afterwards, I did some troubleshooting and the culprit was my propane regulator. The low presure non-adjustable regulators used on propane BBQ's normally work well for forced-air foundry burners, but since mine was built based on a 1" burner tube instead of a wider one, that made the difference. My blower was creating so much pressure inside the skinny tube that it was trying to blow the propane back up the gas line before it could make it into the furnace. When I switched the BBQ reg out for one I took off a turkey fryer kit, that problem went away. It's also adjustable, which is a plus when you're trying to get the right fuel and combustion air mixture.

 

Next post: Not sure, this is the last of the furnace build mini-series. There are still options 2, 4, 5, 6, and 7 from post 8. Or I could show you a little more detail about my oil burner, which I have spoken about just a little in this post. If nobody has a preference, I'll think of something else to post here eventually - I'm always working on something new in my backyard foundry. Thinking about making some more al-bronze stuff, maybe a spear head or a mace or both or something. I also want to redesign my axe pattern with better blade geometry and a wider cutting edge. Maybe I will do that and also modify the one I already have to fix its geometry (it's a little too convex, seen top-down, which can cause it to deflect when chopping at an angle, such as when breaking up big hickory logs as seen above), but keep the small edge and use it to make a hatchet to pair up with the bigger better axe as a matched set. We'll see...

 

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Kang

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Well, I certainly think so...  :)  It's also really shiny in several ways, as hobbies go.  Maybe that's how it has managed to keep my attention...? 

 

Only downside (if there is one) is, it eats up most of my free time, so my life-long minis hobby has been taking a back seat for the past couple of years.  Glad I found this subforum so I can stay involved here somehow, despite not doing as much painting lately!  Not that I was ever the type to crank them out more than maybe a couple a year...  Pretty sure this has been my longest painting hiatus though.

 

I am hoping to work on some minis this winter though, when it's too cold out to want to tinker in my shed and too snowy to want to dig the furnace out of my other shed...  My Reaper purple worm (the metal one that came with an extra tail piece that the plastic ones don't have) is literally green with envy from being ignored. But not quite green enough!  :)

 

Kang

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I'm also finding this neat.  I've been watching a bunch of maker videos recently (mostly blacksmithing and prop making) and this fits right in.  Alas I don't have the time or space to take this up myself but I was looking at making an aluminum foundry at some point.

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It's a lot of fun making stuff. Make sure you do your homework if you decide to go ahead with that at some point though - YouTube is a real mixed bag of amazing knowledge and misinformation that can have a big impact on your success and safety... Happy to share some good reference links and book recommendations if you want.

 

My son has been watching a lot of that show Forged in Fire lately and says he wants to try blacksmithing, which also interests me... So I have probably been watching a lot of the same videos you have recently! :)

 

Kang

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Well, I was at the Value Village this weekend shopping for hallowe'en costumes for the kids. Picked up a used Black & Decker toaster oven while I was there - good deal since it actually still works... I will use it for foundry stuff - baking cores for sand casting, maybe use it as a burnout oven for small lost wax casting molds if they are to be cast in aluminum (which requires a less intense burnout of the mold). Also they had a bunch of those little 3" tall styrofoam skulls. I picked through those and found a couple of them were the type that were sold 2 years ago, which seemed to have been produced using a different permanent mold than the one(s) that make the foam skulls that were sold last year at Michael's - they are a little more realistic around the cheekbones, you can probably see the difference if you look closely at the skulls I cast in the pic above of the snowflake castings; I may have mentioned something about there about how the foam skulls got less good. I haven’t been this year to check yet; I have a bunch of leftover foam skulls in my shed waiting for me to get bored and cast already.

Anyhow, I also did some patternmaking work over the weekend that I will post about, just wanted to dump in a couple pix of my lost foam skull castings that I haven't shown off here yet.

Here is my desk at the day job on Hallowe'en last year. You can see the biggest successful skull casting I have done, a couple of the little guys (one turned into a belt buckle), and a couple of larger failed catsings I thought made suitably scary hallowe'en mutants:

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This one is the best larger sized lost foam skull I have cast. These are fun to make, but they don't make me feel terribly creative since I am just copying cheap seasonal decorations, not creating original pieces. the belt buckles are sort of at l;east halfway creative I guess since the original foam skulls have to me modified in a way I came up with. At any rate, they do get me out melting stuff and pouring metal, that's not nothing...

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(Whoops, the pix are in the wrong order!)

I also have some dollar store Styrofoam jack-o-lanterns that I want to try casting; they are already hollowed out which makes it easier and less of a drain on my supply of meltables. I’ll definitely post about it if/when I cast any of those.

Stay tuned for the beginning of the work I’m doing on my new and improved First Men's bronze axe pattern, which is intended to be half useful tool and half A Song of Ice and Fire fan art...

Later,

Kang

Edited by Kang
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Hey, I was at Michael's yesterday on my way home from the office...  This year they are still selling the not as good 3" foam skulls, but they also have some new Hallowe'en foamies I haven't seen before: quite nice large Styrofoam busts of Frankenstein's monster, some just OK Draculas, and some rather poor looking zombie heads.  Also, creepy wrinkled Styrofoam hands.  They have some nicer Styrofoam jack-o'lanterns than I have seen before too.  And they were all on sale, 60% off...  If there had been prices posted on the shelf so I`d know they'd actually only cost me $3 each, I would have cleaned them out. As it is, I just got a Frank, a Jack, and a Lefty.  I'd like to try and turn my jack-o'lantern into a lamp, maybe with a red or orange light bulb in it, to put out on the front step on Hallowe'en so the light comes out the eyes and mouth, should look pretty creepy if I can get it to work.  Should just be a matter of pushing a piece of tubing through the foam to give the cord a way out of the pumpkin and adding some lamp guts. I guess I'd have to carve an opening at the top like with a real pumpkin to get the lamp parts in and change bulbs, but no big deal there...  I'll be casting them in aluminum.  The lugs in Frank's neck an the stem on Jacks look like separate pieces that have been tacked or glued on to the main foamies, perhaps I will be able to remove them and cast these smaller bits in some different metal to add a bit of colour - brass maybe, or I could use some of my remaining Al-Bronze...

 

Also got some polymer clay to try making some sand casting patterns with for I don't know, maybe some trivets or heating register covers, which was the real reason I went there...  Sculpting with clay-like products will be a pretty new thing to me, assuming it's at least a little different than green-stuffing joints on minis.  I look forward to the experience, and getting a chance to use my new used toaster oven to cure the sculpy-like stuff (I bought the generic brand, much cheaper). 

 

I'll be going back today to grab more Jack's and Frankie's for sure, they seem like fun casting projects and I believe my big crucible is big enough to get the job done.  Who knows, maybe someone else will want one at some point.  Although it may be hard to find time to cast any of this stuff before Hallowe'en.  But if I don't, they can certainly sit in my big bags of foam Hallowe'en stuff until I find time; they'll be out on the front step next year if all else fails.

 

I will post pictures of the foamies when I get a chance to snap a few, and I'll try to take some in-progress pix of the molding and casting etc., maybe even some video if I can find someone willing to hold the camera...

 

Got some progress pix of my new pattern for casting bigger and better bronze axes too, but that is for another post... in the very near future if I can find time to take a break here at some point...

 

Kang

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So. My bronze axe. I'm very happy with how it turned out in terms of the actual casting. But I could have done a little more research about proper axe blade geometry.

 

For instance, the original bronze axe's blade is way too convex. I think this may make it an OK splitter, but this makes it a bit less effective as a chopper - the way the blade sort of bulges out to the sides can sometimes make it deflect rather than biting in...

 

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Also, the sharpened edge is not very long: the whole blade, if sat on its top edge would only be around 2-1/2 inches tall at most. That's because I wanted it to fit through my small band saw when I was cutting out those overly convex curves on the sides.

 

Proper axes are also a little narrower along the top and bottom than they are along the horizontal center line. Because of this vertical tapering, when they grind the edge they have remove material farther back into the blade there to get a consistent bevel to the sharp edge.

 

Time to make a new pattern to address these issues! I did some more research and I have drawn up a new template for cutting out the new pattern. I will get around the limited band saw height by having the pattern split in two during that stage: not just on the mold's parting line like the original, but also at around the midpoint of the blade's height. This way I can cut out half of the blade's height at a time so I'll be able to make a longer sharp ende on it as well as sanding that vertical taper more easily.

 

Here is a pic of the new pattern's paper template sketch cut out and glued to a thin piece of panelling from my scrap bin. I will use this as a sturdier template to trace out where to cut the pine boards I'll use to make the actual pattern for the new and improved axe.

 

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And here's one of the original axe's pattern partially completed, just for comparison and as a reminder of how little actual blade it really has by comparison. I'm not doing the double-bit thing again, although I did make some drqwings that included a better adze blade on the back end. the original was not angled or shaped properly. I'm also not making this one out of MDF, that stuff is easy to work with and has no real grain which is a plus, but it's also prone to warping and is fairly fragile.

 

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Here's the new template roughly cut out on the bandsaw:

 

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Cleaned up on the belt sander:

 

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Flipped over, maybe it's a little easier to see the curves this way...?

 

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I'm making this pattern out of 2 pieces of pine board that are decades old and have been stored indoors so they are nice and straight and dry. Used to be part of my bunk bed when I was a kid, but my kids don't want to use it and it is taking up a ton of space even disassembled... Time to do something with it! Should be good for making a whole bunch more patterns, some 2-part molding flasks, and maybe even a proper molding bench. To make the extra split I mentioned above, I cut each of the two pieces in half lengthwise, then reassembled them with the 2 outside flat finished edges now meeting in the middle

 

With the two pattern-half blanks cut in half and reassembled this way, I drilled some holes through the template and both pattern halves, for alignment dowels. Then I roughly cut out the outline of the template from the pine boards on the band saw and cleaned up the edges on the belt sander:

 

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Here is a shot where you can see the 4 edges that will now be located at the midpoint of the blade (coincides with the longest axis of the pattern due to the curve of the sharpened edge) when the pattern is fully assembled, which I’ll use to trace out the other (hopefully this time not overly convex) template for the band sawing and sanding that will make up the next step. I hope my bandsaw will still make straight cuts when the upper guides are set high enough for the pattern quarters to fit under, this is pushing my saw’s limits a bit, and this strategy of cutting each half in half so they fit is a new idea to me, plus I haven;t had too much chance to really use it very much yet... We’ll see how well it works. Or doesn’t, which would probably mean starting over. Wish me luck!

 

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I have actually done the tracing of the other template on all 4 pieces and have started cutting and sanding one of the quarters to give it the less convex shape, but no pix of that part yet. It's challenging to make all the cuts and sanding be perfectly perpendicular to the flat edges at the pattern midpoint with the limited tools I have. Well, maybe not, but I am sure it would be easier if I had more experience using them. It's really just been this year since I decided to focus on gearing up to do more sand casting that I have picked up my bandsaw, belt sander, and drill press, so I'm still getting used to using them. Things being what they are, this stage of the pattern making is a slow and careful process.

 

Note, this post is much shorter than what I had originally drafted if you can believe that, so if I have edited out any explanations that might have made this more comprehensible and you are interested, please ask questions and I'll do my best to explain. Hopefully the pictures will help...

 

Also, I think I have figured out what I'm going to do with my styrofoam jack-o'lanterns. I will try cutting off the faces on 3 of them and reassembling the faces to make them into one pumpkin with faces all the way around. That way it will make a better lamp since the light will be able to get out in all directions. If I cut them apart between the pumpkin's vertical ridges, it should be easy enough to sand out the seams reasonably well. If/when I go ahead with that I'll definitely take pictures so you guys who are interested can see the process... The downside is, the hot wire foam cutter table I built needs a bit of tuning up before I can do that.

 

Kang

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As promised, my weekend project:

 

- edit - I did not bother fixing up or using the hot wire foam cutter table I mentioned above for any of this.

I took 3 of the styrofoam Jack-o'lanterns I got at Michael's on sale for $3 & change each, chopped off their faces, and glued the faces back together to make one pumpkin with 3 faces going all around... I also glued up a lid piece. This represented most of my free time on Saturday.

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Poured the molds on Sunday afternoon - one for the pumpkin itself, one for the lid. Turns out my #12 crucible holds just enough aluminum for both of these pieces; I had been pretty sure I would have to do a second melt to pour the lid, but I got away with just melting one pot full of hot shiny goo:

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Couple pix of the castings fresh out of the sand:

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Cut off the soup cans, then the big ingots off the top of the sprues. I also cut 2 of the 3 sprues off the pumpkin. I left the stick part of one sprue on each casting for now...

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Clamped those leftover sprues up in the vise to clean up the castings with a wire brush cup drill bit, then cut off the remaining sprues:

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My plan is to drill a hole through the stem so I can hang an orange light bulb inside the pumpkin, but it's done enough to put out on the front step tonight with a tea-light in it... Or maybe I can make a quick stop at the thrift store on my way home tonight to pick up an old lamp to cannibalize for parts, we'll see.

I did get a lot more work done on the new axe pattern, in fact it is almost complete, but that will have to wait for another post on another day…

Anyhow... Happy Hallowe'en everyone!

Edited by Kang
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Wow, this is awesome.  Thanks for sending me here. I'm not sure how I missed this.  Love the bronze bearded axe head.  Your system is so much larger than mine.  My melt furnace will run on 2 propane torches (LOL).  Your furnace is amazing.

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TS, it's not how big your system is... It's how hot you can get it! :)

 

Thanks for checking out my thread, I look forward to seeing your setup in action!

 

Latest thing I've done that relates to red hot metal was cutting up a small disposable type party balloon helium tank to build a propane forge - my 10y old son wants to try some blacksmithing, and that is my kind of father-son project! My charcoal furnace would work just as well with much more capacity, but since we haven't found anything that would work well as an improvised anvil, I figured why not build something I do have the parts for... Still have plenty of ceramic fiber insulation and parts to make a burner for it.

 

I might go to the local hardware store and just buy the biggest sledge hammer head I can find. Embedded into a log, I think the face of that should make an ok anvil surface to get us started with. It'll be handy for work hardening the next bronze axe blade too.

 

Always wanted to try lost wax casting. Until I build a burnout kiln for calcifying investment molds though, I'll have to live vicariously off the work of others like you. When I do build one, I hope to help a friend offer a cast metal option to her life casting business clients. Among other things... Too many projects! Just how I like it.

 

Kang

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Thanks for your intrest.  From your sig it seems like you are interested in machining and machine tools.

 

My first melting furnace, a charcoal fueled monstrosity, was built according to Dave Gingery's book, The Charcoal Foundry. I mention this because that is the first volume in a 7-book series called "build your own metal working shop from scrap" - book 1 is the charcoal furnace, book 2 is the metal lathe, and so on.  It's cool, you build the furnace from book 1 then read book 2 to learn how to make the patterns needed to use the charcoal furnace to cast the parts for the lathe (it actually helps you build itself at a certain point when partly constructed). Then book 3 tells you how to use the furnace and the lathe to build the next machine, and so on.  You get a fully outfitted machine shop by the end of it, although they are lightweight machines and chatter more than real old iron machines.  Some guys on a metal casting forum I frequent were collaborating on making patterns for an improved cast iron Gingery Lathe to share around, but that project has been held up for a while.

 

I have never used a lathe or a milling machine.  Closest thing I have done is to use my drill press to mill out Styrofoam patterns for lost foam casting.  Maybe my next post will be about that process.  But I do find those machines fascinating, I could see myself trying to make the lathe patterns as a long term hobby project.  Some day, maybe...

 

Kang

 

mildly edited for semantic reasons

 

edited again to note that there actually was a machine tool link in the previous poster's sig when I posted this.  I am not crazy.

Edited by Kang
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Just a quick progress update on the new and improved "First Men Bronze Axe" sand casting pattern I am building...

 

I got it all glued together, shaped, sanded, and the core prints attached.  Next step is to hit it with sandable primer then sand it back and hopefully the slight seam between the top and bottom halves will disappear.  Then a coat of spray paint, more sanding, some shellac, more sanding, etc., until it is as smooth as I can get it, so that it will withdraw from the mold without breaking the edges of the cavity.

 

The plan this time is to improve the gating system by creating a runner that leads past the point where a gate will branch off and lead to where the part gets filled up from.  The purpose of this extended runner is to wash any loose sand or dross that might get created by turbulence when the melt hits the bottom of the sprue past the gate so it does not enter the mold cavity proper.  I will also build patterns for the gating this time instead of cutting them in the sand by hand with a spoon - this should reduce the amount of loose sand that will be inside the mold to begin with.  I will also include a bigger riser than the ones on the first axe casting, but just one of them and one gate into the part, not 2 of each like with the first axe (because without the second "bit" the first one had on the back end, there is only one thickest section to feed).  Risers get included in the mold at strategic locations to feed still-molten metal into parts of the casting that freeze off last (due to being thickest or perhaps closest to the sprue), so that those parts do not show shrinkage defects in the finished casting.  Shrinkage comes from thinner sections of the casting freezing first and sucking molten metal from still liquid sections as they shrink upon solidification.  The riser freezes last so that is feeds the last parts of the casting to solidify, and hopefully all the shrinkage occurs on top of the riser rather than on the part being cast.  You can see some good examples of this shrink (called "piping" because of the resemblance to a smoking pipe) on the top of the risers in the pictures from the first axe I cast.

 

But this was going to be a "quick" update.  So.  The pictures:

 

IMG_20161211_225836982_zpso70g7kzz.jpg

 

IMG_20161211_225827172_zpsqmez1unz.jpg

 

IMG_20161211_225904385_zpsfkvwntfe.jpg

 

This wood sure is a lot nicer to work with than the mdf I made the first axe pattern out of!  This axe should be a lot easier to cut firewood with too, or make war on the Childen of the Forest, or really any other sort of popular First Men activities you could imagine...

 

If I have used any unusual foundry jargon ("core prints" frex.), it is probably explained somewhere earlier in this thread.  But feel free to ask questions if these novellas I keep writing are making you go TLDR.  I get it, it is totally understandable; I just can't stop my self from rambling on about this stuff.

 

Kang

Edited by Kang
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Since 2 out of the 3 lost foam castings I poured to give as Christmas gifts were failures, I spent some time yesterday shovelling the snow out of my foundry space so that I can access my furnace and try again, and more time in the evening milling out more Styrofoam patterns on my drill press...

 

Woke up to a blizzard this morning... Some days you just can't win.

 

I'll be doing some more shovelling after work today, I guess.

 

Still a little more milling left to do, but it is quick work working in styrofoam. Then it's just a matter of hot-gluing on some foam sprues and burying the patterns in my sand buckets to be cast ASAP. time is running out but I think I have a decent chance.

 

First fail was a large house number plaque for my sister. Too big, the part of the pattern that was buried shallowest did not fill - I needed a deeper bucket and a taller sprue to create extra head pressure to make it fill. Maybe a steadier pour too - if you let up at all, the sprue can cave in, since the whole mold is just made out of lose dry sand. Sometimes it is hard to see into the soup can with both ends cut off that I stick into the sand around the sprue, because fire and smoke from the vaporized polystyrene is billowing out of the sprue. You don't want to pour too fast either because the can will overflow and you could run out of metal. I should maybe set up a big box fan next to the molds to blow the black smoke away so I can see better or something. Or I could make my sprues out of paper towel tubes wrapped in masking tape so they char but do not vaporize. that also gets the metal to the pattern itself a little faster which is always desirable.

 

Some people coat their foam patterns in layers of thinned drywall mud to help keep them from collapsing. This is a backyard caster's imitation of the ceramic shell* coatings used for lost foam casting in industry (such as in Saturn's lost foam cast engine blocks, the unmachined surfaces of which clearly show the beaded Styrofoam texture replicated in cast aluminum), but that takes so long, and the being able to go from carving foam to pouring metal the same day without having to wait for coatings to dry is the main reason I use the lost foam method in the first place. A trade-off between reliability and speed, I suppose. To try again and have cleaned up castings ready to give out on Christmas, I do not have the option of waiting several days for layers of mud to fully dry, so I am committed to bare-doggin' it (technical term) once again at this point. I think my bucket of mud is frozen solid right now anyhow...

 

Second fail was a portrait plaque of my son for my parents. Daughter came out great, but I thought I had enough metal left in the crucible to pour the second one. I should have put it back in the furnace and melted more, that is what happens when you rush things I guess.

 

I made the portrait plaques by converting digital pix into 3-toned (highlight, midtone, shading) "pop art" style graphics through a website, then milling out the midtone 1/8" and the shading 1/4" out of a piece of 1" thick blue insulation Styrofoam board with the printout glued onto it. The plan was to paint the shading black, leave the midtone as-cast, and give the highlight some sanding and a quick wire brushed finish. I have done this once before with only 2 tones to make a portrait of my wife's grandmother and I must admit it came out a bit creepy looking, but the 3-tone version of my daughter came out quite a bit nicer I think.

 

Here is a pic of the kinda creepy one to give an idea:

 

IMG_0534_zpsibzjeg00.jpg

 

My solution to the house numbers was to just cast the numbers themselves, rather than cast a large plaque. That way I can lay the foam numbers on their sides and have plenty of height to work with.

 

I hope I can get them all done in time! Plan is to pour either tonight or tomorrow afternoon. Nothing like leaving things to the last minute! Could be I will be one of those guys doing the frantic last minute shopping in crowded malls on the 24th, but I really hope not. I have cut some of my waste veg oil fuel with some diesel, in hopes that it will flow well despite the cold weather. Wish me luck!

 

Pics of these latest ones will have to wait, I don't have access here...

 

Kang

 

* - ceramic shell is also commonly used in lost wax casting like Talespinner is getting all set up for over in the sculpting subforum, but with his vacuum-assisted casting rig, I believe he will be using more traditional plaster(like)-based bock investment, not ceramic shell..

Edited by Kang

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