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Crucible Sizes?
Hello, folks. The last time I posted here, I was casting zinc arrow
heads. Recently, I have been hanging out with lead bullet casters. And now it looks like I need to learn how to cast brass. The reason is because I want to build a bottom-pour pot. I already know from experience that when working with zinc, I need to deal with the dross in one way or another, and, when working with lead, I guess I will run into the same problem. Anyway, I have decided to try to build a bottom-pour pot, in order to deal with the dross problem. What I have in mind is to melt some brass, and then to pour it into an open mold, the bottom of which will be the bottom of my cast-iron melting-pot, on the out side of the pot. The sides of the mold will be something like a tinker's dam, I guess you could say. I will clean the bottom of the pot first, because, of course, I want the brass to stick to the bottom of the pot. After I've got a big lump of brass which is stuck to the bottom of my melting pot, I will then drill a couple of holes through it, to give me my spout, and my valve (with a bolt, to finish the valve). Okay, so the problem is that I will need to select a crucible which will be the right size for me to melt the brass, and then, by the way, I will design a furnace to fit the crucible. I will be firing with charcoal. Okay, so can somebody give me an idea about crucible sizes? I really don't have a clue! Two states have already outlawed lead wheel weights, and I want to get some lead casting in while I can. Mike Mandaville Austin, Texas |
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#2
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Crucible Sizes?
On Tue, 14 Jul 2009 09:14:20 -0700, in rec.crafts.jewelry Muso
wrote: Okay, so can somebody give me an idea about crucible sizes? I really don't have a clue! Um, not to state the obvious, but your crucible needs to be large enough to hold the amount of brass you're melting... Since you've not given us that information, how can we give you more? This isn't complex. Crucibles don't come in millions of sizes. Find a supplier of the types of crucible you're planning to use, and pick a size from their offerings that is large enough... Many crucibles sold for jewelry melting will specify their size in capacity for a certain weight, of a given metal. To convert that to capacity for a different metal, like brass, divide the original capacity figure by the specific gravity of the metal they're using as the specification, and then multiply that result by the specific gravity of the metal you will use (brass). The result is the crucible's capacity in a weight of brass. Beyond that, you need to choose a crucible material. Choices include solid (machined) graphite, a clay/graphite mix (black crucibles, but not machined, more like a clay pot in how they're made) or various sand/clay mixes, or the higher temp fused silica ceramics. I'd guess one of the cheap clay/sand types, or clay/graphite ones, would work fine. Also. If you wish your poured brass to fully adhere to the iron pot, you'll need to do more than just clean it. molten brass poured onto cold iron will seperate again, because of thermal shrinkage as the brass cools. Even with good bonding from the brass "wetting" the iron, this may be an ongoing problem in use. But with a good active soldering flux on the iron (after cleaning), and preheating the iron before pouring the brass, the two should braze together. You may wish to experiment a bit with a small piece of cast iron first, to be sure this will work. It's not as straight forward as it may seem. Cast iron can be tricky stuff to bond to. One potential solution, maybe, would be to not rely totally on metal/metal bonding, but rather, to also drill and tap a couple screw holes from inside the pot into the brass, and hold the two together with a couple screws too. Or, you could just go and buy a bottom pour crucible... They're not all that expensive, last time I looked. Which was a while ago... Peter |
#3
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Crucible Sizes?
Muso wrote:
Hello, folks. The last time I posted here, I was casting zinc arrow heads. Recently, I have been hanging out with lead bullet casters. And now it looks like I need to learn how to cast brass. The reason is because I want to build a bottom-pour pot. I already know from experience that when working with zinc, I need to deal with the dross in one way or another, and, when working with lead, I guess I will run into the same problem. Anyway, I have decided to try to build a bottom-pour pot, in order to deal with the dross problem. What I have in mind is to melt some brass, and then to pour it into an open mold, the bottom of which will be the bottom of my cast-iron melting-pot, on the out side of the pot. The sides of the mold will be something like a tinker's dam, I guess you could say. I will clean the bottom of the pot first, because, of course, I want the brass to stick to the bottom of the pot. After I've got a big lump of brass which is stuck to the bottom of my melting pot, I will then drill a couple of holes through it, to give me my spout, and my valve (with a bolt, to finish the valve). Okay, so the problem is that I will need to select a crucible which will be the right size for me to melt the brass, and then, by the way, I will design a furnace to fit the crucible. I will be firing with charcoal. Okay, so can somebody give me an idea about crucible sizes? I really don't have a clue! Two states have already outlawed lead wheel weights, and I want to get some lead casting in while I can. Mike Mandaville Austin, Texas After about 30 seconds of searching I found you a bottom pour melting pot for $56.95 at http://tinyurl.com/m9zedt Do you really think that you can make your own melting pot, by way of making your own furnace first to melt the brass, for less than $56.95 The materials alone will cost you more. And how many hours are you willing to waste to get you a result that will not work nearly as well as that pot I just showed you? As you said yourself, you really don't have a clue. Oh, and to answer your question re. the size of the crucible. Have you possibly considered for a moment, that it should be big enough to hold the amount of brass that you plan to melt. -- Abrasha http://www.abrasha.com |
#4
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Crucible Sizes?
In article , Abrasha's reply
included, from anothher poster: "Two states have already outlawed lead wheel weight" So I ask, slightly off topic: What are using,then, uranium? Regards to you all, G.H.Ireland -- _ _________________________________________ / \._._ |_ _ _ /' Orpheus Internet Services \_/| |_)| |(/_|_|_ / 'Internet for Everyone' _______ | ___________./ http://www.orpheusinternet.co.uk |
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