Home made cast Aluminium

[John PParticipant @johnp77052]

Hi Chris
I was given the cast wheels they are about 56 mm diameter about the
same size used in the Wren 54 turbine engine.

The wheel on the left is for a KJ 66 size turbine and was milled on the Dore Westbury
cnc machine ,seen here was a test cut in wax.

John

[jann westParticipant @jannwest71382]

Would someone be so kind as to private-mail me a link to the original video which generated so much discussion – just so I can see what generated the big discussion … thanks – Jann

[I.M. OUTAHEREParticipant @i-m-outahere]

Hi Jann ,

You have a PM in your inbox .

[I.M. OUTAHEREParticipant @i-m-outahere]

Well Rob has been at it again and in his latest video he uses an old slave cylinder as a mold – worked well but he used alloy of an unknown grade and although it cast ok it didn’t machine well so his trick of using old mag rims is something one should stick to if they want Bar stock that machines ok .

[SillyOldDufferModerator @sillyoldduffer]

Surely this is a case of expectation management?

If a bunch of unknown Aluminium scrap is melted the resulting metal won't be to an engineering specification. Unknown composition and not heat-treated to recover properties lost in the melt. Quite difficult to fix in an amateur foundry because few home workshops have the necessary equipment to heat-treat Aluminium – it needs a temperature controlled soak.

Doesn't mean casting Aluminium is a waste of time. Although home-made castings can't be top-notch, could still be fit for purpose. Casting safety critical parts in a shed would be insane, but provided the limitations are recognised, casting Aluminium seems a good wheeze to me. Castings are useful even if they are a bit soft, slightly weak, and don't machine particularly well.

Same objections apply to home-melted cast-iron being a flawed material, but many find that worth doing.

Can't think of a good reason for not trying it.

Dave

[Neil WyattModerator @neilwyatt]

I'm reluctant to add anything to what John has said as he has much real world experience and skill in aluminium casting and I have only played around with small castings in brass and white metal.

However, I do understand that most aluminium alloys 'age hardening' at various different rates and some do so at normal temperatures so don't lose heart is a casting appears delicate at first, it may well become stiffer at room temperature on a scale of hours to weeks depending on the mix.

Some types machine better when still ductile, others are sticky like pure aluminium. All I can suggest is that a bit of experimentation may be in order, and if your original source material was nice and hard then the result may well age harden without intervention.

Neil

<edited to qualify that only some alloys age harden at normal temperatures>

Edited By Neil Wyatt on 30/08/2020 11:34:29

[Bill PudneyParticipant @billpudney37759]

Apart from the satisfaction of actually making an ingot of al.alloy, I really cannot see the point. If you want to make something from an al.alloy it might be worthwhile being aware of the difference between annealed and heat treated conditions for two of the materials mentioned earlier

6061 T0 ult. (ksi) 18, yield (ksi) 8, hardness 30 (Brinell No, 500kg load, 10mm ball)

6061 T6 ult (ksi) 45, yield (ksi) 40, hardness 95 (Brinell No, 500kg load, 10mm ball)

7075 T0 ult (ksi) 33, yield (ksi)15, hardness 60 (Brinell No, 500kg load, 10mm ball)

7075 T6 ult (ksi) 76, yield (ksi) 67, hardness150 (Brinell No, 500kg load, 10mm ball)

So, in broad terms the annealed material, apart from being pretty poor to machine would possess approximately 50% of the ultimate strength, 20% of the yield strength and the hardness would be significantly less for both.

Now obviously this will not matter if all you are making is a name plate, but if you are planning to make something strong and light (after all this is what Al. Alloy has been developed for) you may be kidding yourself. No doubt lots of people will chime in with "Well Fred Bloggs made a phoo phoo valve from rescued material, and it works just fine" Well good for Fred would be my response.

cheers, and the very best of luck

Bill

Edited By Bill Pudney on 30/08/2020 12:19:48

[ChrisBParticipant @chrisb35596]

Of course you will not be using the cast aluminium for aircraft parts, I would imagine that's clear to all. That does not mean it does not have it's use tho, I normally use aluminium for ease of machining and where strength is not a critical requirement. I have a block of 7075T6 alloy which I use sparingly for special projects. Knowing how expensive the material is I don't want to waste it.

As for heat treating, if you have a pid controlled oven it would not be so difficult to do. Would definitely like to try it out.

[JasonBModerator @jasonb]

The point seemed to be cost saving. For something like an engine bed or just a block to use as a one off jig or arbor this source would be fine.

Chris, this one popped up on Youtube today

Edited By JasonB on 30/08/2020 13:25:08

[ChrisBParticipant @chrisb35596]

Yes Jason, that would be similar in principle to what I had in mind and it looks like it works. There are some things I would do differently especially when it comes to electrical safety but the principle is the same.

Posted by JasonB on 30/08/2020 13:24:09:

The point seemed to be cost saving.

Edited By JasonB on 30/08/2020 13:25:0

I had already purchased all the material needed for the furnace quite a while ago to build a heat treat oven. They have sat there ever since collecting dust! A project for the coming winter, summer to unbearably hot here to be spending any length of time in the workshop

[I.M. OUTAHEREParticipant @i-m-outahere]

One of the channels i subscribe to who has also watched the video on casting has made a video on how he made his funace – Thought it might have some useful info for U.K forum members .

https://youtu.be/vYXWm1WnpLo

I had a look at his video list and he doesn’t do reviews as far as i could see but he does give a few links to the materials and burner he used I believe both are legitimate retailers .

Hope it passes scrutiny !

[BazyleParticipant @bazyle]

A lightly odd shape for that electric furnace and unnecessary cutting of corner pieces but the subsequent links on youtube had some better designs.
Electric casting inside would be nice in terms of using the expensive heat resource a second time to heat the house but ooh the fume and fire risk. A subsequent heat treat oven however would be viable.
Beer keg version really takes it down to simple. I think I will be going round the car boot sale next week with a different shopping list from normal. Being rural there is never any machine tools but lots of kitchen stuff.

[ChrisBParticipant @chrisb35596]

Posted by Bazyle on 31/08/2020 10:32:58:

Electric casting inside would be nice in terms of using the expensive heat resource a second time to heat the house but ooh the fume and fire risk. A subsequent heat treat oven however would be viable.

I could be wrong but I think running the oven on electricity might work out to cost the same or I dare say even cheaper than if run on LPG. Locally the cost of electricity is 0.13€ per kwh, the cost of LPG is 0.09€ per kwh. But, a pid controlled oven will reach the set temp and regulate where as an LPG furnace will (normally) not regulate, so it's either full blast on or off – add to that a slight inefficiency in the combustion and the cost of running will – I think – be fairly close to each other.

But I could be wrong!

[BazyleParticipant @bazyle]

Chris, my electricity in the UK countryside is twice that except ont eh cheap rate overnight. A heat treat oven on a timer overnight would be viable and bonus of a nice warm workshop in the morning – if I didn't have to go to work. But you could get it 'free' from solar panels, or a nice challenge (for you) would be a mirror based furnace.

[not done it yetParticipant @notdoneityet]

electricity in the UK countryside is twice that except ont eh cheap rate overnight.

Bazyle,

1 1/2 times, maybe, but not that much if on the right tariff. As long as one avoids the possibly elevated prices between 16:00 and 20:00h, those on the Octopus Agile tariff have usually paid considerably less than 18p/unit (inclusive of VAT) for other times during the day and most of the night.

Further, there is 5 hours (I think) during the night when unit charge is just 5p (before VAT). Some on the Octopus Go tariff have received ridiculously low bills (single digits/month) – even while charging a BEV during the night and sometimes during the day when they were actually being paid to use as much electricity as possible! – as much as 3.5p for every unit consumed.🙂

Standing charges can make a large difference to energy costs in the UK, depending on the energy used, so the simple comparison is perhaps not so clear but for this comparison, standing charges can be ignored.

My current tariff is a tad over 15p for daytime units and a tad over 10p for E7. We are low energy users and this year the change was likely to be not worth changing (no smart meter installed and gas prices need to be taken into account, too). Next time the tariff changes, I expect to move to Octopus unless my current supplier gets more competitive.

[PatJParticipant @patj87806]

I have been tinkering with backyard casting since 2011, and have poured aluminum and gray iron successfully.

I started out with just stacking hard fire bricks in a circle, and using a propane burner, to melt aluminum 356.

Aluminum 356 is pretty good metal, but untempered it is a bit gummy to machine.

If you put 356 in a kiln and hold it at the right temperature (I think 1,000 F was the setting) for 8 hours, followed by a hot water quench, and then 4 hours at 400 F, you can approximate a T6 temper, and that material machines very nicely.

Many use old potter kilns as furnaces, but be sure to turn off the mains before reaching into the kiln, else contacting one of the elements could be rather shocking.

The spilled metal tends to destroy the elements, and the elements can be prone to breakage.

I have not used a kiln to melt metal, since the process can be a bit slow, such as perhaps 1 hour for a crucible of aluminum.  I can melt a #10 crucible of aluminum in 12 minutes flat using an oil burner, but most use propane to melt aluminum, and propane works very well too.

You also have to be very careful not to overheat aluminum, since that seems to cause it to absorb a lot of gasses, which create bubbles in the casting, or pinholes I guess.

If you use quality 356 stock, and don't overheat, you can get quality castings without any degassing or flux.

I decided to learn how to cast gray iron, and that was about a 6 year process.

I finally figured it all out, and can get most excellent iron castings consistently, with no defects and easy machinablility.

Gray iron is ideal for engine work, and I am really glad I figured out how to make those castings.

My ytube channel is here:

No advertisements or endorsements whatsoever in any of my videos.

https://www.youtube.com/channel/UC9dVr4EIhHcFLIz0xY2bEXw/videos

Edited By PatJ on 05/11/2020 06:56:51

[grimmeParticipant @grimme]

Posted by I.M. OUTAHERE on 25/08/2020 11:51:45:

That video tweaked my interest also !

A simple furnace made out of a paint tin lined with pearlite / cement mix , a crucible made from an old oil filter housing and the mold is just seem less steel pipe . From one mag wheel you get a fair bit of aluminium .

played around quite a bit casting ali, dross/ inclusions are the pain, but not the main one! i melted casting from the scrapyard which didnt look right, it seemed to be twinkling, so shut off and took the crucible out, on contact with the air it turned into a 4ft roman candle which burnt for 15min until it subsided enough for me to dare to pour it out on the dry sand tray, what over flowed onto the ground then splutterd and fired off like an old riprap firework, im guessing that it was a magnesium fire and hms shellfield catching fire in the falklands war came to mind. i only melt pistons now

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