Metal Casting Zone

Morning, I have a simpleish question. I need to be able to so some machining. I cannot afford 500+ for a lathe, so I have decided to make one. That lead me to metal casting. Using investment casting, or lost foam casting, I can make whatever the hell I need and only have to pay material, and fuel costs. Hell, I even enjoy this kind of work, so that is an added bonus.

My question is what do I use to make a crucible cup from that can withstand weight, heat, and me? From what I have seen, you use graphite, fire clay, and some other stuff. My primary concern is the damned thing breaking and spilling molten steel/aluminum all over the damned place. Can I just hit that with a hose, or will it explode?

Before any of you start with "You should start small" I am, I have a store bought crucible that will be arriving today, and it will only hold a pound or so of aluminum. I will be playing with it a lot, but it ran me 25 bucks, and I am adverse to spending money I do not have to. A crucible big enough to do what I want is expensive, and I like being able to choose the size and design, and make it custom for my furnace... Which will also be custom.

It needs to be able to handle steel, and aluminum, about 10 pounds to start, but I will need to upgrade to 25 pounds later.

Hi xarlock667,

If you are going to make machinery like a lathe you would be beter off with cast iron, and for large melts I would sugest you build a cupola.
Have you read many/any books on the subect? A good starting point is "Foundrywork for the Amateur" by Terry Aspin No 4 in the Workshop Practice Series. Dave Gingery wrote a series of seven books "Build Your Own Metal Working Shop From Scrap" I Have not seen these so can not coment on their content or quality howeve the titles cover makeing a foundry, Lath, shaper , mill, drill press, acessories, and sheet metal break. Vince Gingery has writen "Making Crucibles",another book I have not seen.
Your libary should be able to help with some information if not these titles.

Do Not Put Water On Molten Metal it will Explode!!

Peter.

Howdy! FWIW, I have the Gingery series and highly reccomend it. I am in the process of building the lathe (been in progress for nearly two years, I gotta finish it at some point) and I have the crucible book, too. Follow the instructions, and you will have pretty good results.
Just for safety sake, I wouldn't go much larger than an A10 size crucible for a homemade, they don't last as long as commercial ones, and large ones are more difficult to fire. Besides, you REALLY need to be able to trust your crucible at that large of a melt. Do you really want to have your crucible crack full of molten iron just as you are removing it from the furnace? something to think about.

I wasn't clear enough. I need a recipe for making a crucible that will hold up to a largeish casting of iron/aluminum in the 10 pound range. This is not negotiable. I have to have that large of a casting in order to do the lathe bed, head stock, tail stock, etc...

I don't need a list of books. I need a practical recipe that is based on user experience, and that has been used successfully in the past with repeated results. I have books, a great number of them. Books are wonderful for teaching concepts, but not so wonderful for actual implementation. If something is not working out, I cannot ask a book what went wrong. If I wanted to just use a book I would not be on an online forum asking questions.

Do not get me wrong I do a hell of a lot of research in books, more than is probably good for me, but that is not what I need here. I need a recipe, and feedback if I screw up to tell me what I did wrong.

xarlock667,

Sorry for the misunderstanding. My experience with home made crucibles is limited. For aluminum and brass I use fabricated steel, usually a large pipe with a disk welded to form the bottom, these I line with ganister. I have made crucibles for iron from leftover refractory from making the furnace, only one of these has been used so far and on the second melt a large fissure formed releasing half the melt into the furnace. I put this failure down to (1) my not having the refractory perfectly formed and (2) my use of lime stone flux which I think eroded the crack. My failed crucible was capable of holding over 10lb of iron, I have made another which should hold 25lb of iron however I do not anticipate using it any time soon.

As you have books I suggest you try the formulas from them. Nothing will teach as well as experience.

How is the casting going with your $25 crucible?

Peter.

How about titanium?
I heard that it is a better one for large casting?


sell gold

Graphite SUCKS in a charcoal foundry. It is eaten SO fast that it is not worth the expense.

I have actually switched to a piece of 3" diameter steel pipe about 8" long with a simple pipe cap secured to the end. Secured TIGHTLY. For aluminum, make SURE it is rust free, or you will get a taste of thermite and die painfully. A wire brush works well for this.