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Author Topic: Casting and getting white metal to flow?  (Read 2771 times)

craggle

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Casting and getting white metal to flow?
« on: March 16, 2013, 07:41:37 PM »

Hi All


I made a mould today on my milling machine to cast some rubbing strips for my tug boat. They are a shallow "D" section 6mm wide and 2mm thick. I made the mould in the side of a aluminium bar using an 8mm bullnose cutter and cutting to a depth of 2mm.


I was going to pour resin in this mould but then thought, wonder if white metal would work so I found some low temperature metal I have and heated the mould on a hot plate and when the metal started melting I poured it into the mould but it didn't really fill the void, just stuck in a string like shape down the middle.
I played with the metal for some time spreading it about and then finally adding more metal than needed, removing the mould from the hot plate and dropping another aluminium bar on the top effectively squashing it into the mould.


I now have the parts I need that will be perfectly usable with a skim of filler and a sanding but has anyone cast metal before and have any techniques to get it to flow better or was I using the wrong material really?


Cheers


Craig.
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grendel

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Re: Casting and getting white metal to flow?
« Reply #1 on: March 16, 2013, 07:53:29 PM »

I have always carved my moulds into soapstone for casting white metal, the moulds generally work best when they are two part with a pouring hole, and when the moulds are pre heated to at least quite warm, I use a candle to deposit  thin layer of soot inside the mould (this helps air escape and acts as a release agent) sometimes you need to cut additional air channels to help the metal flow, usually the first few mouldings are rubbish until the mould heats up, just throw the metal back into the pot and re-melt.
my source of soapstone was to find a shop selling soapstone figures from africa etc, then go in and ask if they have any breakages in transport, usually you can get them for nothing or at least very cheap. (crocodiles cut in half lengthwise are good for long moulds) you can do open topped moulds, but the backs may need sanding to make them flat.
really its about trial and error, and being prepared to make mistakes - at least with white metal its fairly forgiving, one source for metal is old lead free pewter tankards, you can pick them up at jumble sales and boot fairs dirt cheap if you take the dented ones.
Grendel
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grendel

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Re: Casting and getting white metal to flow?
« Reply #2 on: March 16, 2013, 08:11:12 PM »

heres a few of my old moulds I have dug out - mostly viking age belt fittings, but they were what came to hand first, you can see the soot discolouration and fine air channels here anyway as well as the pouring spout, I used to do some of these at re-enactments, using an open fire to heat the metal in a ladle, just holding the two halves of the mould together (wearing welders gloves), after a few seconds the metal has cooled enough to see the results.

Grendel
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grendel

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Re: Casting and getting white metal to flow?
« Reply #3 on: March 16, 2013, 08:13:52 PM »

soapstone has the advantage it can be carved easily - a penknife can do it. I used to use fine woodcarving tools.
Grendel
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eddiesolo

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Re: Casting and getting white metal to flow?
« Reply #4 on: March 16, 2013, 08:23:46 PM »

Interesting Grendal. Not that I would do any smelting but the info you provided is very interesting indeed, no need for expensive moulds etc.
Si:)
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grendel

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Re: Casting and getting white metal to flow?
« Reply #5 on: March 16, 2013, 08:32:27 PM »

great for small production runs of simple items, before that I use to buy the moulds for white metal figures and cast those, so carving my own moulds was a simple step from that.
Grendel
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craggle

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Re: Casting and getting white metal to flow?
« Reply #6 on: March 16, 2013, 09:26:29 PM »

Thanks Grendal


Lots of useful tips and none of which I would have thought of myself.  :-)
It was good fun today playing with the metal and the mould and seeing what happens and what makes it worse. I did learn that plumbers flux makes it worse!
I'll try to find some soapstone and have a play with that in closed moulds rather than my open top mould version of today. Guess I can machine soapstone too if it's that easy to carve.

Thanks for the information, Lots of knowledgeable people on this site.  :-)


Craig.
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Jerry C

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Re: Casting and getting white metal to flow?
« Reply #7 on: March 16, 2013, 10:30:33 PM »

When casting bullets, (lead, tin and antimony mix) always used tallow as flux causing mix to flow smoothly into mould.
Jerry.

grendel

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Re: Casting and getting white metal to flow?
« Reply #8 on: March 16, 2013, 10:35:22 PM »

the trouble with aluminium is the heat is dissapated too quickly for the white metal to stay molten long enough to cast smoothly, unless you have the mould up to the melting point of the metal being cast. soapstone is basically solid talcum powder, talc can be used in rubber moulds to allow good metal flow (allows the air to vent).
soapstone should machine very well.

Grendel
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craggle

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Re: Casting and getting white metal to flow?
« Reply #9 on: March 16, 2013, 10:44:13 PM »

I did have the aluminium mould sitting on an electric hotplate and it was hot enough to melt the solid metal by touching it on the mould. Your right though, aluminium is a great heatsink so I can see the moulten metal solidifying as soon as it touches it otherwise.


I'll try to find some soapstone and let you know how it machines.


A friend of mine mentioned Tallow today Jerry as he used to cast his own fishing weights with off cuts of lead flashing. He's a builder, he didn't get it from the church roof! Not something I keep though Tallow so couldn't experiment with that.


Cheers


Craig.
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PW569

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Re: Casting and getting white metal to flow?
« Reply #10 on: March 16, 2013, 11:57:47 PM »

Hi!

The only casting of metal I did was as a child. Tin Soldiers. In the Rubber molds I always used talcum powder as a flux (or was it to get the figures easy out of the mold or preserve it?).

Another thing I noticed was the mix of the white metal. As the stuff sold in the toy shop was too expensive, I went to the local plumbers and got what they used on gutters.
However, it was not as good as the stuff offered in the toy shop...i.e., with the expensive stuff let's say every second try was good (like fully casted sabre of the riding  soldier) while with the "industrial" stuff it took many more efforts! But his may only play a role when it comes to fine detail. I never measured the temperature of the metal, but to heat it a little more seemed to help back then!
So, having said that, there may be different qualities out there, some better suited for casting than others! But I do not have the knowledge on what is best...

Soapstone! GREAT IDEA!

Cheers!
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grendel

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Re: Casting and getting white metal to flow?
« Reply #11 on: March 17, 2013, 12:31:55 AM »

lead free pewter melts about 20 deg C higher than most other white metals, but does give good castings from my experience, plus its fairly easy to get in the form of the newer old pewter tankards.
Grendel
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grendel

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Re: Casting and getting white metal to flow?
« Reply #12 on: March 17, 2013, 12:34:05 AM »

Oh the soapstone - that was how the vikings would cast metals, they would also use cuttlefish as moulds, nothing new in this world, and at times the old ways work best.
Grendel
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PW569

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Re: Casting and getting white metal to flow?
« Reply #13 on: March 17, 2013, 12:39:45 AM »

Grendel?

cuttlefish??????????

Is there something lost in translation, or do you really mean squid?


I mean, HOW? :o

Cheers,
Lars
 
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grendel

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Re: Casting and getting white metal to flow?
« Reply #14 on: March 17, 2013, 12:49:26 AM »

the boney plates that you feed budgies and parrots, you carve your design in and pour in the metal, as far as I know they are only any good for one off's, but they can be used for bronze.-
http://www.codesmiths.com/shed/things/smithing/casting/
Grendel
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PW569

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Re: Casting and getting white metal to flow?
« Reply #15 on: March 17, 2013, 12:54:25 AM »

Stupid me! Of course! That makes sense! For some reason I thought about the jelly parts.... %%
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vnkiwi

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Re: Casting and getting white metal to flow?
« Reply #16 on: March 17, 2013, 04:29:04 AM »

Just rub some talcum powder around the inside of your metal mould.
It allows the air to escape, and always over fill your mould a bit.
cheers
vnkiwi
ps, its why the cuttle shell works so well.
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