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Grahame Collins
23rd Aug 2015, 12:13 AM
Hi Guys,

I am posting a question here in the hope someone may have experience or knowledge of the following.

I am interested in casting some aluminium around the tang of a self made knife to create a handle. I know this can be done as it is a production technique to speed the mass production of commercially made knives.

There are 2 piece metallic moulds clamped around the tang as the knife is held vertically and the pour completed from the top of the tang end.

The question regards the material type of the 2 piece moulds.On the video it looks to be an aluminium colour .I realise it could not be that as the molten metal would melt the mould of the same material. Is there a similar alloy with a higher melting temperature suitable to make the mould from.

The mould material is reminiscent of fishing sinker mould metal.

I am seeking something like that to reduce the work in cutting the shape of the mould.

Heres the video, the casting happens at around 4.14 minutes.

https://www.youtube.com/watch?v=lBKnLe7tYmU

And a couple of screen shots to see the shape and colour of the mould materials. 357343 357344

Michael G
23rd Aug 2015, 10:19 AM
I did put a post up suggesting that the handles were a zinc alloy, but the video definitely says Al and it looks as if it is (although the stills are not as clear). The dies look like Al too.
Al will melt at different temperatures depending on composition, so pure Al melts at 660 degrees C and the addition of alloying elements will lower that - the mould could be made of pure Al with another alloy (say melting point 630 degrees C) used to pour. The dies are also have a bit of mass to them so pouring in hot metal would get them close to melting but the cold steel tang and cold mould would take up some of the heat and drop the temperature rapidly. Interestingly he drops the mould into a water bath after use, so it has gotten warm...

I do wonder what they will do when Granddad's milling machine collapses. It's looking a bit shaky there in the video.

Michael

Grahame Collins
23rd Aug 2015, 01:11 PM
I did put a post up suggesting that the handles were a zinc alloy, but the video definitely says Al and it looks as if it is (although the stills are not as clear). The dies look like Al too.
Al will melt at different temperatures depending on composition, so pure Al melts at 660 degrees C and the addition of alloying elements will lower that - the mould could be made of pure Al with another alloy (say melting point 630 degrees C) used to pour. The dies are also have a bit of mass to them so pouring in hot metal would get them close to melting but the cold steel tang and cold mould would take up some of the heat and drop the temperature rapidly. Interestingly he drops the mould into a water bath after use, so it has gotten warm...

I do wonder what they will do when Granddad's milling machine collapses. It's looking a bit shaky there in the video.

Michael

Agree about the moulds for not only the colour and that the nature of the scuffing and dings in the external surfaces suggest Aluminium. Maybe an alloy of copper and aluminium. I'll do some research on that.

But for grandad Rudy's purpose built milling machine, I'll cut him a bit of slack. It's not half bad for something the old chap designed and is still producing after 3 generations. The narrator-one of the grandsons- mentions how the old boy put it together from scrap and that it creaks and groans but keeps on going.

Grahame Collins
27th Aug 2015, 10:39 AM
A quick follow up for those so interested.

It seems the moulds were aluminium. The high heat transfer ability transfers the heat away .As observed in the u tube clip the used moulds are allowed to cool on the concrete.