Picture of Aluminium Foundry
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This is my second Ible of my homemade foundry. My first one was my :
Mini Charcoal Furnace.

In  this instructable I will explain how I made my second bigger foundry yet again mostly constructed from scrap I collected and recycled it into something more usefull.
The biggest advantage of this design is that it has a very strong body made from an empty gas cylinder and the best part is that it will last for a long time, the only thing that might have to be changed or repaired is the inside refractory.
 As I wrote on my last ible my aim is to create some aluminium sand casting of differrent objects.
At this stage I piled my aluminum ingots and did a few experiments with my foundry, some successful others went wrong which I have learned from. It is really exciting to create some new aluminium object knowing what it was in its former "life" cycle.
I will also try and explain a little bit about sand casting to my knowledge.
I am no expert it is all based on my hobby experience so I  hope you enjoy it.

A few Saftey words:
 Coming  into contact with fire and boiling melted metal can be very dangerous so always work safe using proper full body protection including respirator mask against toxic fumes and dust from mixing refractory materials. Never melt in a wet area or near water, if water comes into contact with the boiling aluminium it might "blow" in your direction.
The info in this instructable is based on my experience. 
I disclaim any responsibility for any resulting damage, injury, or expense.
All use by you of this website is at your own risk, work safe.
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afridave10 days ago

i like...but im not so sure about attempting to cut a gas bottle open......

stansell2 months ago

Hello! Brilliant instructable, but i'm having some trouble understanding the final section about sand casting.

How did you get from the 5th to 6th photo? they seem to be very different. Also the 7th to 8th photo seems very different - how do you get from one to the other?

Kevanf14 years ago
Excellent ible. Trouble is, now I don't know whether I want to make a stove for my workshop or a furnace suing the old gas bottle I have :)

I have a question if I may? Do you have any problems with the surface of your castings? I need to make some aluminium moulds (for pouring molten lead into for fishing weights) but they really have to be nice and smooth. Any ideas how I can achieve this?

Take care.

NutandBolt (author)  Kevanf14 years ago
Thank you I am happy you liked my ible. The best way to decide is which one will be more useful in the long run. Most of my  castings are very good. I had of course some casting gone wrong but usually the reason is running out of aluminum, bad mould construction, porosity (small gas deefects, air holes) or just doing some experiments. I am using petrobond sand for my moulds and it's great sand to work with and to get very high quality finish.
You are welcomed to visit my blog I have a few projects using sand casting. I believe you can get very good results using this type of sand and you can make a mould for many fishing weights in one pour.
Just one thing and this is up to you to decide, I wouldn't melt any lead at all,  Lead is a poisonous metal and can cause serious health problems especially among children. Link:
Lead health effects
 If you have any questions I will be happy to answer thanks again.
You would have to heat lead up to an insanely high temperature (3180F!) to have any dangerous effects from casting it. Just don't eat it and wash your hands.
I have to tend to agree with 'klincecum' here, sorry 'NutandBolt'. Most people who cast lead fishing weights do tend to do it outdoors or at least with very good ventilation anyway. So there's no real health concerns with it. I suppose there may be secondary risks from using scrap lead though. Unless you know for certain that the lead has not been used with nasty chemicals next to it. I'm thinking lead pipe work that is used for chemical transference. That could cause problems....
Hiya mate. Just noticed something, I am not 'suing' any old gas bottles :) I will be using them of course...

Anyway, Petrobond sand. Any idea what makes it special as opposed to ordinary sand. It sounds like a trade name and it's not one that I know of here in the UK. I was thinking of using what we call silver sand. This is a very fine and very clean sand that is used for children's sand (play) pits. It has to be fine, soft and ultra clean because of this. I'll add fuller's earth clay to this to create my moulding sand but don't yet know in what quantities.

Lead. Yep, nasty stuff but then so is aluminium fumes. Lead casting is quite common still over here in the UK and I will only be doing it outside. There are still an awful lot of houses that have lead water pipes ours included. Having once been a plumbing and heating engineer I can tell everybody that the danger from lead is real but very much overstated. It's bad if you ingest it in anyway and that does indeed include fumes, hence my proposing to cast the weights out of doors, it's safest that way.

Thank you for the health warning though it is appreciated :)

Take care.

NutandBolt (author)  Kevanf14 years ago
Petrobond vs green sand. petrobond is oil-bonded casting sand, theoretically you can leave the sand in a closed container and it will be good for use years later. Also the final casting will be very high quality. The downside: it is expensive in comparison to green sand. Play sand is also good but you have to make sure you make a good mix ratio of the play sand+Bentonite(clay)+water (not too much water). Petrobond is available in the UK and is mostly sold in foundrys and less in hardware shops such as B&Q. I know that because the petrobond I have is made in the U.k. I am not promoting products but this is the link of the commpany   in case you want to have a look.
petrobondJW (Small).jpgpetrobond.JPG
Fantastic :) I'll e-mail the company and ask if they can give me a list of stockists (local hopefully as we do have the odd foundry still dotted about).

Thank you and take care.

RingoWild1 year ago
I know how thrilling it is when you try something and it works so well! What a great feeling. Congrats! But what is petrobond?
Could you tell me exactly what refractory you used? I am having an extremely hard time finding a good tutorial on refractory, and would be extremely grateful.
Great job...! Thanks for the Instructable... I will try out the aluminium forging some day. Make spare parts, machine them, and plate them with copper,nickel, or chrome :)

SLaorr2 years ago
Big fan of the project! I'm thinking about doing it myself. Now, I know you mentioned what size bag of cement you got, but how much did you use? I'm trying to be economical and I want to get the smallest size I can for this design.
hriosm3 years ago
Be careful. I heard sometime you shouldn´t use old tanks because of something could explode besides the gas.
Schmidty163 years ago
very cool u will have to sell ur alimuium and can u melt steel with it or what about gold or silver
n1cod3mus3 years ago
learned something a few days back, dont use charcoal briquettes they produce too much ash which clogs up the air flow, use lumpwood charcoal burns nice and hot with much less ash.
zomfibame3 years ago
I'm digging your hinge design. and the whole thing is very nicely done.
i found the hindge method good as well but i didnt want to reach over the furnace even with gloves. so i made a pedal lift lid

I have heard that a lot of blues and yellows in paints have cadmium in them, thus their names...
www.backyardmetalcasting.com and the sister site www.alloyavenue.com will provide as much information as you can use and can answer almost any question you may have on the subject !!
bherrboldt3 years ago
Again you rock. I have done 2 melts and poured 24 aluminum ingots. Im going to pour more tomorrow and then I think i will be ready to sand cast. Thanks again.
I've actually done the same thing (with a propane tank that is) Very nice job! I ended up scrapping most of it, because I couldn't get a decent enough mold to make it work. But I've never heard of petrobond. Then again, I built the whole thing for <$50 because I was on such a tight budget...

One thing I would recommend though is that you modify it a bit and put a propane burner in instead. Much easier than charcoal, and you have a more controllable heat. From the looks of yours, all you would have to do is insert a propane line into the blower pipe, and you're pretty much there. You would just need to add a flame holder, but that's fairly simple.

Very well done!
For decent molds, I would highly suggest trying out lost-foam casting. You can do it with junk Styrofoam and an X-Acto knife or something similarly sharp, and sand from your backyard. It's just about the cheapest and easiest method to produce fairly high-quality objects.
rhulett13 years ago

How long is the inlet pipe ?

Is the length critical ?

Is the flange important ?

Great job.....Roger
EmmettO4 years ago
As for crucibles, I struggled with making a crucible for melting copper. It would melt through every steel crucible I made. I eventually found a site that sells cheap fire clay crucibles and thats what I use now. http://www.lmine.com/mm5/merchant.mvc?Screen=PROD&Store_Code=LMS&Product_Code=17703&Category_Code=economy_repacks
i got mine for around $60 at foundry101.com and it comes with a lifting shank..
Omnombulist3 years ago
Wonderful ible! I just finished making a similar furnace and will be adding a hinge after seeing how nicely yours worked. I used regular portland cement and cured it for 18 days before firing. It is pretty thoroughly covered in hairline cracks after 4 firings and the outside gets terribly hot. I am guessing I will have to recast the cement before too long and am interested in fire cement.
How well Is your refractory holding up? How many times have you fired it?
bherrboldt3 years ago
All I have to say it thank you so much. I just built my refractory/foundry almost exactly like yours. All I have left is to get ahold of some refractory cement and Im in business. This is awsome. You rock!
imbignate4 years ago
Firstly, what sort of sensor are you using for a temperature gauge, and where is it mounted?

Second, what are you using as a mold for the ingots? They're all a nice standard size and very professional.

Third, this is awesome.
NutandBolt (author)  imbignate4 years ago
The sensor I used is a simple and trusted multimeter that I got on Ebay. All that is needed is to set the multimeter setting to tempature and place the tempature wire in the furnace.
As for the ingots, I am using metal muffin tray (not teflon). All you have to do is pour the molten metal into it and you get a nice aluminum muffin. You can also make a container for the ingots DIY style like the one I welded from metal angles. I am using it to make slim ingots for my pipe cruicble.
Thank you.
Nice technique with filling the gas cylinder with water! An elegant solution to the problem of flammables. 

A professional iron worker once told me that cast iron cookware works well for a crucible. There are a variety of pans, pots, "dutch ovens" and other styles to choose from. Maybe there are cast iron muffin pans waiting to be found at a junk sale.

NutandBolt (author)  DIY-Guy4 years ago
Thank you, That is correct I heard the same thing regarding cast iron cookware used as crucible the only thing is finding the right size that will fit into my furnace ;-)
Check out the book by David Gingry. Then you can make your own cast iron cricible
just so you know it's Gingery, not Gingry. :-)
Details, details. And I suppose you want a crucible instead of a cricible?
I have been warned about using cast iron cookware if it has not been cleaned of all rust. If I understood correctly, what I was told is the combination of rust and molten aluminum can form something akin to thermite (possibly thermite itself?). If this is the case it could be very dangerous.
Ferrous oxide (rust) and aluminium do make thermite. Although the exact ratio's are industry secrets for each company they boil down a lot of rust powder and a lot of aluminium powder mainly for surface area considerations (occasionally it is doped with magnesium to help things along). At any level of rust build up on a pot that doesn't affect it structurally I don't think you have much to worry about. I've never had a problem. but if your worried put the offending rusty item in the smelter with it going full bore for a few minutes (be careful cause this smelter can easily melt cast iron if you are using charcoal ... I speak from experience of loosing an entire melt to this whoops(!?!)) by the time the pot has a barely visible glow in normal light there will be no more rust on it.
cendit4 years ago
I can´t see if the refractory partially blocks the air inlet. I'm asking in case that is some kind nozzle, because the area reduction. Thanks
Doddity4 years ago
My dad recently got several dead lawnmowers from junk heaps.
I repaired the oldest one and we are restoring it but he tore the rest apart for the pistons and such that he uses to make statues.
The rest of the mowers were set to be thrown out but I grabbed a large amount of aluminium pieces. Just testing my furnace i threw a chunk in and it melted beautifully and was quite strong when I later pulled it out.
I recommend saving them and smashing the cast base into smaller pieces as well as the tougher engine pieces.
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