Crucibles

[Artie]

Gday, fire clay itself really isnt up to the job as we have already established, and needs several additives.

You can buy and weigh in these additives individually, or you can add 60% silica sand to the fireclay which has the bits we need in it already. This is the simplest way...

heres a vid with a simple crucible recipe...

The best bit about casting is simply making up stock for use in machining, I have every size stock you can think of available to me...just gotta warm of the f(l)oundry... good luck and have fun....

Sorry link has issues, just follow it to youtube....

[ame]http://http://www.youtube.com/watch?v=E3my6-nxFjM[/ame]

 

[Artie]

Thought this may be of interest to some, my foundry is very very old (nearly 30 years) and is showing signs of age and trauma, cracks and crumble. It was also originally coke fired and therefore has a large internal volume which is now wasted and inefficient since I converted it to gas.

so Ive been thinking about a replacement and the next one will be based on this vid. You could make timber molds for the bricks... Although I would make the base in one piece as well as the top ring, in case you bump it lifting the crucible....

[ame]http://http://www.youtube.com/watch?v=VA9MLQJM3u0&feature=related[/ame]

 

[gus]

When replying to a question I try to give relevant , safe , advice always based on my own experience and not on what I have read somewhere.
The question was "what is the best crucible for melting brass" not aluminium.
Even though it is common to melt aluminium in a steel pot I would not recommend it unless a suitable internal wash has been applied.
Steel dissolves readily in molten aluminium , not only contaminating the melt but gradually weakening the container.
You would wear the correct protective clothing for any hazardous operation , why skimp on the tools ?

May I add on my 2 cents worth plus my real life experience or near disaster.
30 years ago,I had to bid for an order of 100 air compressors which had to had an aluminium condensate trap. Had watched my uncles casting aluminium using book molds and kerosene fired CI crucible.

We got the order. Built a gas fired furnace and used a length of steel pipe as crucilble. While degassing with chemicals and grain refining during the 6 casting session,the aluminium ate through the steel pipe.Fortunately nothing spilled out.

Went over to have foundries to make me a cast iron crucible. And it survived many sessions.

If you are not too fussy and small CI camping pot will do with LPG stove.

But please be forewarned,aluminium casting is not for the total green horn.
Melting aluminium in the open air is dangerous when it rains.Aluminium scraps must be bone dry------no water.


Gus from faraway Singapore.

 

[blighty]

Aluminium scraps must be bone dry------no water.

what if you have a bit of WD 40 on the scraps/swarf. as i have a bucket under my power saw that the swarf falls into. as i give the blade a shot of WD every now and then the ali swarf in the bucket is covered in oil (not dripping, but a light covering). will this just burn off..... or explode in my face?

 

[Artie]

what if you have a bit of WD 40 on the scraps/swarf. as i have a bucket under my power saw that the swarf falls into. as i give the blade a shot of WD every now and then the ali swarf in the bucket is covered in oil (not dripping, but a light covering). will this just burn off..... or explode in my face?

The no water thing is only true IF you are adding the swarf to a hot crucible.. if you are packing a cold crucible the water wont hurt as it boils off, just exlodes (almost) if added to a hot set up. So wd40 will be no problem IF its a cold crucible.

The problem with swarf is 2 fold, firstly a fully packed crucible wont yield much metal, you will need to repack it when its melted down (swarf has little actual volume but it needs to be DRY) and the amount of slag you will get due to the large surface area of the partially oxidised metal.

Id use swarf to fill the gaps in the crucible when melting other lumps down (over time).

 

[gus]

Thanks for the treasure trove of info especialiy the websites. I must stress again,backyard casting is not for green horns. For those who want to do casting at home,may I suggest buying some sinker molds and practise casting lead sinkers. Lead has very much lower melt temperature.

Gus did some casting of aluminium.I was a green horn but I did exercise extreme caution.After five years of occasional cast to make air compresssor auto condensate traps by the hundreds using compressed air aided molds and not a single accident. It was very hot and uncomfortable to cast in hot,wet and humid Singapore. I will post foto of traps made and possibly the near professional aluminium furnace I built.
I am grateful to my "uncle" in the neighbourhood foundries for let me watch them melting and casting aluminium for many occasions and asking endless questions when I was a 12 year old kid..These uncles read aluminium temperation and book mold temperature by eyeball. I did ask them in later life why they did not use pyrometers when I was doing engineering school.
Take great care when casting metals.

 

[blighty]

The no water thing is only true IF you are adding the swarf to a hot crucible.. if you are packing a cold crucible the water wont hurt as it boils off, just exlodes (almost) if added to a hot set up. So wd40 will be no problem IF its a cold crucible.

The problem with swarf is 2 fold, firstly a fully packed crucible wont yield much metal, you will need to repack it when its melted down (swarf has little actual volume but it needs to be DRY) and the amount of slag you will get due to the large surface area of the partially oxidised metal.

Id use swarf to fill the gaps in the crucible when melting other lumps down (over time).

Artie,

thats a sham about not getting much from re-melting swarf as i have been saving it up for a year. all up i have about 10kg of mill, lathe and band saw swarf and a bucket full of off cuts.

i'll give it ago any way, see what i get in the end.

 

[Artie]

Artie,

thats a sham about not getting much from re-melting swarf as i have been saving it up for a year. all up i have about 10kg of mill, lathe and band saw swarf and a bucket full of off cuts.

i'll give it ago any way, see what i get in the end.

I guess its relevant to how you look at it. 10kg of swarf would be a pretty big volume, it comes down to how much can you pack into a crucible, Ive done it before, FILL the crucible with swarf, melt it down and you've got half a cup of melt, yes you have 10kg of swarf BUT it'll take a lot of melts to get 8 kilo of metal... cause thats how much slag you may find (depending on the metal you are talking about).

I melted a 20 litre bucket of brass chips down once, that worked ok because it was chips and not swarf so it packed in fairly tight.

Noones saying it wont work, just dont be surprised at the work involved...

There is only one way to be sure and thats do what you say, "give it a go". If we all believed only what we are told, we would never actually 'do' anything... let us know what you are melting and how you get on.