anachronism

Discussion in 'New member introductions' started by anachronism, Sep 8, 2019.

  1. Hello all. It's nice to be here. I've been looking at non-ferrous casting for a while, both as a hobby, and as a potential source of additional income. This will be my first step into the big league, I've been a bullet caster for many decades and now its time for me to apply myself to new challenges. I hope nobody minds a bunch of dumb questions...:)
     
  2. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    Welcome to The Home Foundry. What type of castings interest you and what are you thinking as far as foundry equipment?

    Best,
    Kelly
     
  3. Primarily brass and aluminum. I plan to start out with some basic sand casting of larger pieces before I progress to frustrating myself with smaller more intricate designs. I've been following myford on Youtube for years, and now I feel I'm comfortable enough with things to graduate to the bigger steps. Things like, building a furnace. I've seen some really simple designs out there but I'm stuck at the most basic question- how big of a furnace to build? I don't anticipate doing anything really large, but I'm hoping to pick up some ideas here.

    I decided that the 5 gal. can size would be too small. It would work at first, but not allow any room for growth without replacement. I have a couple of 15 gallon size oil drums the I'll likely use but I'm unsure about how thick the walls should be. I plan to pour the walls using refractory and a vibrator to help minimize air pockets. Since I have no plans to do iron (yet) I'm thinking that 3 inch thick poured walls should be sufficient. I'd appreciate any input anyone may have on this. I'll be starting out on propane and reevaluate that idea when I see how bad my fuel costs are :). I almost broke down and bought a ready made commercial furnace, but I had a short burst of mental clarity and called the seller and asked the dimensions & capacities of the unit. It was 11 inches high and about that in diameter. Probably okay to play with, but no room for expansion.

    Thanks!
    Bob
     
  4. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    You don't want 3" of dense refractory because that would be a lot of mass to heat and most hobbyists only pour once or twice per furnace heating cycle and spend as much or more on fuel to bring their furnace to temperature as they do to melt metal. The most common furnace has a dense refractory hot face (say <1") and several inches of refractory wool. That would give a 3" wall. If you are familiar with Myfordboy that would be similar to his furnace. I'd suggest 1 1/2" gap between the wall and crucible for tong/tool space. That says the OD of the furnace shell is 9" greater than the crucible you want to use.

    That style of furnace is time tested, though I must say, you should also consider the thin coated hot face over refractory wool approach such as FishbonzWva advocates:

    http://www.alloyavenue.com/vb/showthread.php?13570-A10-Satanite-Furnace-Build&highlight=satanite

    ...and more recently Tobho Mott did this build. They are easy to build, very low mass, inexpensive, efficient furnaces and well suited for propane. They are also comparatively very light weight so easier to set up move and store.

    http://forums.thehomefoundry.org/index.php?threads/another-lightweight-fiber-blanket-furnace.726/

    Best,
    Kelly
     
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  5. Hi Bob, it sounds like you have a good idea of what you want in the way of a furnace. It may be a good idea to get hold of a suitable sized crucible and work back from there as depending on where you live as crucible supplies can vary a bit. I designed for an A20 crucible and found that I had to buy an AT30 to get one in silicon carbide, this meant extending the height of the furnace to fit it in. If you're pouring brass/bronze solo, you'll have to size the crucible for what you can safely lift. I have a friend with a A30 crucible sized propane fired furnace with three inches of dense refractory and it works great, but is fuel hungry and the outside of the furnace reaches 680 deg F / 360 deg C. This is in an industrial setting with a large commercial 460 lb / 210 Kg gas cylinder.

    Edit: as Kelly says, it's a lot of mass to heat and a hot face over refractory fibre is going to be much more efficient.
     
    Last edited: Sep 8, 2019
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  6. Jason

    Jason Silver Banner Member

    I like Bob already! That was my dads name and this Bob already knows it's a furnace, not a forge or a metal foundry!
     
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  7. Much to learn here, I seem to have made a good choice in coming here. I also have a new word, plinth! With most new sites, the best I can hope for is to remember my password:). Here, I already have homework! It's ironic that Mark suggested starting out by buying a suitable crucible first, then building the furnace around it. I've had this nagging feeling that I was approaching this project backwards, and now I'm sure that this is what I was actually doing. I had to sign up at AA so I could blow up some of the pics shown. And Kelly is already saving me money and headaches. I was figuring on up to three bags of refractory for the walls. In my area, refractory is about $60.00/bag, and if I did use three bags, the furnace would weigh over 150 lbs. Does anybody have any vendor recommendations? I really don't want to buy any more through ebay than absolutely necessary.

    Jason- that's my bullet casting history talking there. All this is a far cry from my PID controlled lead furnace, and my PID controlled heat-treating (modified toaster oven) oven. Another irony here is that new members are at the "lead" level!

    Thanks again!
    Bob
     
  8. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    If you have a local supplier of refractory material identified, that's a big step up because shipping on refractory materials is often as much as the material itself. You'll need to tell us specifically what material you seek and how much you need. If you don't want to buy off eBay or Amazon, you may need to buy quite a bit more material than you need. I could recommend an eBay source unless you are just sick of the whole eBay thing (and I get that).

    These folks have been good to members for small quantities and are sort of the go-to source for the brush on Satanite hot face coating but they are quite high on wool/ceramic fiber in quantity.

    http://www.hightemptools.com/supplies.html

    There are many online sources for wool. Quite a few sources for castable refractory too but shipping is quite expensive on the latter.

    Best,
    Kelly
     
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  9. My local Menards has two 50 lb bags of medium duty refractory in stock. The brand is "Akona", and it's rated over 2500 degrees. I see Satanite is rated at 3200 degrees. Is there a significant difference here? I still have an active ebay account, I've just grown a little weary of them.

    Hmmm... Kellys in Iowa, and I'm in Nebraska.

    Thanks!
    Bob
     
  10. My keg based furnace is using 4.5 x 25 Kg / 50 lb bags of refractory for an AT30 sized crucible and that's with 65mm / 2.5" thick refractory. It's around $60 per bag delivered to my door, I did miss out on some free bags at a nearby sugar mill that was relining their boiler by a week or so, they tossed out the excess unused bags when finished.
     
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  11. Jason

    Jason Silver Banner Member

    Yup... Always crucible first! When you get your refractory, plan on casting up a couple of plinths at the same time. Think cool whip container size. It should be tall enough so when your burner is running, you are not hitting the crucible with the flame. It's a rookie mistake that's easily prevented.

    Next new word for you is TUYERE. Pronounced two-yair. This is the hole in which you plug your burner in. See how knowing the height of your plinth with help you in positioning the hole in the side of your furnace for the tuyere? Read the last sentence again until it is crystal clear. Refractory cement is miserable stuff to hog out if you F this up! So DON'T! ;)
    I drink Shiner-bock btw.:p
     
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  12. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    I actually have a local company that supplies refractory materials to foundries and the metal heat treating industry so I am incredibly blessed that regard.

    When I hear you say Menard's, I would say it's very low probability they have the materials you'd prefer. Dense or insulating fire brick and common refractory cements? Yes. Good castable refractory....no. Look for local companies that cater to foundry, heat treat, and boiler furnace maintenance.

    Best,
    Kelly
     
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  13. Petee716

    Petee716 Silver Banner Member

    Welcome Bob,
    Ask a bricklayer or boilermaker of your acquaintance if they know any refractory guys. I had a chance conversation with an old friend I used to rip and run with when we were kids and it turns out he's a refractory bricklayer. He had bags of the stuff in his garage and was making garden decorations out of it.
    The advice you've gotten here is top notch. I built my last furnace several years ago out of a beer keg. I used 1-1/2" 30:60 mix of fireclay and sand for a backer and then faced with 1" of 3000 deg Mizzou (Harbison-Walker). I bought pieces of heavy guage duct 10 and 12" diameter at a HVAC supply place for the forms. I ended up with a 10" bore. I use waste oil so I don't really mind the added fuel consumption on the initial heatup, and the furnace weighs several hundred lbs. Given that the materials cost me very little I have no regrets. However if I were to do it again I might very well go the ceramic wool/Satinite route. These have proven to be very effective and durable furnaces without all of the (literal) heavy lifting and expense of folks acquiring multiple bags of refractory.
    I agree that other than playsand and hard firebricks, any materials you buy from menards or other big box stores will not stand up to what you're about to throw at it. That refractory might be fine for fireplaces or maybe a pizza oven, but not metal melting furnaces or forges. It may be tempting but you'll have to trust us on that one.

    Pete
     
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  14. Tobho Mott

    Tobho Mott Silver Banner Member

    Welcome to the forum!

    I have a big myfordboy-ish style 1" dense refractory and 2" ceramic fiber blanket furnace, and a smaller fishbonz' style 2" ceramic fiber with a thin layer of Satanite furnace. For doing single melts on the weekend, I'd pick the latter every time if I didn't need the extra crucible space that my bigger furnace allows, because from a cold start the small furnace heats up and melts the first crucible of metal so much faster. But I expect I'll be having to patch it up a lot more often. Still too new to known that for sure though, really. I've never had to do any repairs on the big furnace which I've had for 4 years now, though I'd say it has only seen casual use... All it has are a couple of hairline cracks that it's had since I first fired the refractory. It would be my choice if I wanted to spend all day pouring castings - once it finally gets up to temp, it should work just as fast as the little one, would hold its heat much better between melts, and it is far more durable. However, with the Satanite mortar used in the low mass furnace, patching is super quick and easy, so that's not really a big issue. The little furnace can also easily be picked up and tossed in the trunk of my minivan, whereas I think I might need a forklift or at least a couple strong guys helping me out if I ever wanted to get the big furnace into, say, the back of a pickup truck.

    Petee does have the 3" thick all dense construction furnace he described above, and Rasper has one like it as well for bronze casting that he swears by, saying it never ever cracks. But they both definitely use oil burners on those furnaces, not propane ($), and they saved bundles by making the outer 2" or more from a sand and clay mixture instead of using a couple extra bags of expensive castable refractory each... plenty of ways to skin a cat as they say, but the "best" way largely depends on what type of fuel you prefer and how often you think you will be using it.

    Oh, and there are also insulating castable refractories such as cast-o-lite 30. I haven't tried it, but a furnace with a 3" thick wall of that stuff might not take forever to heat up like dense castable does. I don't recall anyone here using it, but IIRC (someone correct me if I'm mistaken) one of dallen's iron casting furnaces was built that way. He's a member on AA but I don't think he's been active there recently. He's the guy who helped out with building YouTuber SVSeeker's oil burner and furnace several years ago, those videos might also be worth a look if you haven't seen them, as that furnace is a really sweet piece of work.

    Jeff
     
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  15. I've discovered that one of the large concrete plants in town stocks refractory. I'll be going there Saturday to see what they offer. I am also interested in the oil burner approach, but I need to do more research on it since I've never tried building one before.

    Kelly- I was admiring your big furnace build, man the engineering in that setup is really impressive. I really like your shop as well, a very nice setup to be certain.

    Meanwhile, I continue cruising the internet, and ebay too. My plans are gelling nicely now, just a few more details to work out before I dive in. But first, crucibles.

    Thanks again,
    Bob
     
  16. Jason

    Jason Silver Banner Member

    Bob, At your stage of the game, the only real difference between propane or an oil burner design be it, waste veggie oil, used motor oil or diesel... Oil burners require a bit more breathing room around the crucible compared to propane. On propane, you only need enough room for your lifting tool to pluck the crucible out when it's hot. So if there is a possibility you will end up not running propane later, build it with about 1.5"-2" of space between the largest crucible you'll use and the inner walls. Savvy?

    I started with an oil burner and only screw with bronze. I think propane is expensive and a pain in the ass. For small melts, it's fine, but for longer melts, the oil burner shines. I've got mine working happily on just jet-A with NO PROPANE PREHEAT! Diesel or Kerosene would do the same thing and is cheap as chips. Plan for around max 3gallons of fuel per hour. Still pretty damn cheap compared to a round of golf.
     
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  17. OMM

    OMM Silver Banner Member

    I personally think crucible is second or maybe even last. Crucibles don’t jump up too much in dia. size to match inside diameter, but their height does.

    Usually consumables are what you throw away. Some here might consider a furnace a consumable.

    I would figure out your torch, then figure out the maximum size furnace you are comfortable with. Going smaller is not a problem if you went bigger to start,....wishing you went bigger results in a new build.
     
    Last edited: Sep 11, 2019
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  18. FishbonzWV

    FishbonzWV Silver Banner Member

    Hi Bob, welcome to the world of melting metal.
    There's been three experienced people recommend building an energy efficient furnace. Let me be the fourth.
    There's two on this forum melting cast iron with this style.
    I've built two Satanite/wool furnaces. The first was an A6 size and I used it for 4 years and over 200 melts and it looks the same now as it did on day one. I can melt a pot of Aluminum for around 60 cents worth of propane.
    The second was the one Kelly referred to. It weighs 37 pounds. Uses about a dollars worth of gas.
    With a furnace of this type a propane burner is all you need.
    You can build a wool furnace in a weekend instead of a month using castable refractory.
    My analogy, it's like a Tesla vs a Model A
     
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  19. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    Good luck. Cant beat cash and carry refractory materials.

    I think it comes down to what's convenient, economical, what and how much you want to melt. If you have a large furnace and will be melting iron, and have access to free waste oils, free fuel can be a big factor, and there is a lot of energy available in waste oils. But often this requires transport and storage of fuel. If you live in a rural area and already heat your house with propane or natural gas, that's also pretty compelling......or just buy and use diesel as you go. There's a little more development and fuss with oil burners but once you get your routine sorted it wont seem significant compared to other factors.

    Thanks Bob. I tend to go overboard on builds but I also love to build and fabricate.......good therapy.

    I can buy most refractory materials at my local source. It's always a small fraction of what any other source would be with shipping. I could also order any material I wanted through them but I only do that very sparingly as I don't want to become a burden. I have an account with them and they treat me well.

    For crucibles, I use Morgan Super Salamnders. They are clay graphite and great all around items. They are always consistent size which matters once you build your handling tools. A word of caution though, there are counterfeiters on eBay and internet. These are two eBay sources that are authorized Morgan dealers. I've bought from both of them. I probably use an A10 for 90% of my work. Compare at delivered prices.

    https://www.ebay.com/itm/MORGAN-SAL...0rZ5TNtKpyZQ:sc:FedExHomeDelivery!52722!US!-1
    https://www.ebay.com/itm/A-10-Cruci...787118&hash=item2eb40c87c4:g:X60AAOSw4a1bUg2j

    There are certainly other manufacturers and sources but with care and aluminum duty, I expect low 100s of melts before replacement.

    On specialty materials not stocked locally, I've used these three on occasion.

    https://www.ebay.com/str/hightemperaturematerials
    https://www.ebay.com/str/hightemprefractorystore
    https://www.ebay.com/str/simondstore?_trksid=p2047675.l2563

    I think you can bypass eBay and buy from them all direct if you search.

    Best,
    Kelly
     
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  20. Petee716

    Petee716 Silver Banner Member

    The guys are giving you (us) some good stuff here Bob. On the crucible first or last topic OMM brings up a good point. You'll find most furnaces here tend to be 10-12" bore. Some bigger and some smaller, but that's pretty average. My first furnace was 8. My next one was 10,. I wish it was 12. See where I'm going here? It's nearly impossible to know all that you'll be casting, but you have to start somewhere. My largest crucible is a number 18 from Legend Mining. That's 18 kg of copper. Not all manufacturers label their capacities that way so be careful when ordering. Anyway, that just barely fits my bore and allows for tong insertion into the furnace. Use density formulas to figure out comparative volumes to aluminum. When you guess the volume of metal you need add another 25% to that volume to allow for gating. You can put a too-small crucible in your furnace, but not a too-large one. Height is another factor. You want your tuyere to come in a couple inches above the bottom. The tuyere usually ends up being around 2" in diameter or so and you need your crucible to sit just above that so your flame isn't directly hitting it. Others seem to be observing that having the crucible higher in the available space in the furnace, within a inch or two from the lid, is optimal. Melterskelter has demonstrated this but for me to say it's so would be talking out of school. At any rate your crucible sits on a plinth, and having plinths of varying heights will allow for different crucibles. As Kelly mentioned, the #10 is my workhorse. My smallest crucible is a #8.
    As a side note, you absolutely must have your crucible in-hand before building your lifting tools. There's little to no wiggle room there.

    Pete
     
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