Casting gear blanks from scrap aluminium

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Ike Turner
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Location: Victoria, Australia

Re: Casting gear blanks from scrap aluminium

Post by Ike Turner »

ctwo wrote:Ike, I just bought a 1/2" plate of 6061 aluminum for under $20, enough to make five 4" gears.

Try this calculator for the weight/volume

http://www.custompartnet.com/quick-tool ... calculator

That is one very handy online calculator.
I hadn't thought of buying material in plate form, will have to look into it.
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Pipescs
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Re: Casting gear blanks from scrap aluminium

Post by Pipescs »

Offering an alternate solution

Instead of using a iron pot with a wash, could he not have a local potter make him a clay crucible.

I originally bought a set of crucibles from Budget Casting. Once I got them they did not look right. It turned out they were not Graphite-Clay but just clay. Budget assured me they would work for the brass and bronze in my future.

They have been in use sporadically for the last year and a half or so and this is the results.

The one on the left has been used for aluminum and the one on the right for brass which needed more heat and a longer firing.
DSC_1475.jpg
DSC_1476.jpg
I have since ordered new Graphite-Clay ones and am retiring the one on the right to the trash but keeping the one for the aluminum.

Could he not go to a local potter and work something out.
Charlie Pipes
Mid-South Live Steamers


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Harold_V
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Re: Casting gear blanks from scrap aluminium

Post by Harold_V »

Charlie,
Those are graphite/clay. That's why they're gray/black in color. The upgrade would be to move to silicon carbide crucibles, which are colored darker, and a little more shiny (the glaze alters the appearance somewhat).

Clay in and of itself would not be very stable. I've used clay dishes in the melting of precious metals and they're a bear to use, cracking very easily. That's not a quality you'd want in a crucible full of molten metal. By sharp contrast, the graphite/clay is much more stable, with the silicon carbide crucibles offering much lower cracking issues upon heating.

So long as you season a graphite clay crucible, it should provide quite decent service. Seasoning involves the slow heating, to drive off residual moisture, before taking the crucible above the boiling point of water. That's particularly important for those who live where there's a lot of atmospheric moisture, as they absorb the moisture readily, even after having been used.

By the way, the crucible you intend to discard appears to still offer life, unless there's something I can't see. Might as well wring a few more heats from the thing, if possible.

Fluxing is very hard on crucibles. They'll degrade rapidly with its use (that's what flux is supposed to do---remove impurities and cause the metal to flow better), but it often can not be avoided. Borax isn't very aggressive, but if you use soda ash, they'll be destroyed rapidly.

When I melted recovered silver, flux was essential. I got only about eight heats per crucible, due to the dissolution of the walls above the metal line. I went through a large number of both types of crucibles.

Harold
Wise people talk because they have something to say. Fools talk because they have to say something.
Ike Turner
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Re: Casting gear blanks from scrap aluminium

Post by Ike Turner »

I have discovered that there is a foundry supplier quite close to where I will be working next month; hopefully I'll be able to obtain a suitable crucible from them, may even buy some petrobond and make a flask to do the job with a little more finesse than just pouring molten aluminium into an open tray as I had planned. In the meantime I'll try a few engine reconditioners and see if I can obtain a suitable quantity of used pistons for raw material.
Suitable aluminium in plate form doesn't seem to be available in anywhere near 1" thickness, so purchasing some plate stock doesn't seem to be an option.
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Harold_V
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Re: Casting gear blanks from scrap aluminium

Post by Harold_V »

Ike Turner wrote: a little more finesse than just pouring molten aluminium into an open tray as I had planned.
Be VERY careful about pouring molten metals on to ANY hard surface which may contain moisture, and metal most certainly may. The resulting steam explosion can be quite interesting.

If you pour to a metal form, ensure it's dry by heating beyond the boiling point of water.

Harold
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steamin10
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Re: Casting gear blanks from scrap aluminium

Post by steamin10 »

My Compliments to Harold, his experience is similar to mine.
Pipescs: Unless you developed a crack or something not seen, you are at the point where I would lay in a new vessel while I continued to use the last of life there. Being a basic cheep guy I used my vessels down to absolute scary looking before they were discarded. They are still safe as most of the wear is focused on the rim that thins to a fair the well. If you are making tiny heats, (I dont recommend) the flux line will go thru the side at some point, forcing replacement.

I try to never melt less than half a vessel, the overage poured into a bar or stick for for lathe stock or pretty discs. If need be they can be reverted to the next heat.

Once again, I never pour on concrete, it expodes with a spill. I have a sheet 4x4 of 3/4 plywood that gets an inch of sugar sand, that molds are layed out on. Any spillage just hardens off and cools to be picked up. Another trick is to press a bar shape into this sand and pig excess right there.
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Pipescs
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Re: Casting gear blanks from scrap aluminium

Post by Pipescs »

Hey all, Thanks for the input on the flask.

My thought on their being clay only is based on the below, which is the disruption of the Flasks in the 8 range offered by Budget Casting listing the material used to make them. This is cut an pasted from their website.

#5080 B8 Clay-Graphite Bilge $74.50

#5081 B8 Silicon-Carbide Bilge $157.00

#5082 A8 Clay A $35.50

Having said that, they did come black and went gray after the first firing.
Charlie Pipes
Mid-South Live Steamers


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Scratch Built 3 3/4 scale 0-4-4 Forney
Little Engines American
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Metalman
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Re: Casting gear blanks from scrap aluminium

Post by Metalman »

I am curious and possibly missing something here but if the goal is making change gears from aluminum why cast the metal? Is there no suitable alloy available in plate or billet that could suit the purpose?
Ernie F.
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Pipescs
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Re: Casting gear blanks from scrap aluminium

Post by Pipescs »

Your question is very appropriate. It would be very easy to order the plate to do it with and rough cut the blanks with a band say

The issue can be cost. Having a furnace and the ability to cast "Blanks" or Rods can be a cost saver.

A good example is these valve push rod valve gland.

I went out looking for a piece of bar stock to machine them from and found prices in the 60.00 per foot range for brass or bronze.

I ended up using my waste oil furnace to cast a billet from 2.00 per pound scraps and then machined the glands from that.

Total time on the pattern was an evening in the shop.
DSC_1186.jpg
DSC_1185.jpg
DSC_1189.jpg

Casting time was two hours, Cost to run a waste oil furnace was Zero.

Having a furnace capability in your shop can open a whole new world for a modeler. It will definitely make you think out of the box.

This is a charcoal furnace using an electric leaf blower for air. I understand it is over 40 years old. I have seen it melt 15 pounds of Brass/bronze in 30 minutes for the cost of a big bag of charcoal.
IMG_0057.JPG
It produced this in an afternoon.
IMG_0063.JPG


The patterns for gear blanks can be done in an hour and the casting in an afternoon.

Old Pistons, engine blocks or transmission cases can be found in just about any junk yard in the world.

It will be interesting to see how he tackles this beast.

Keep the photos flowing on it.
Charlie Pipes
Mid-South Live Steamers


Current Projects:

Scratch Built 3 3/4 scale 0-4-4 Forney
Little Engines American
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Harold_V
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Re: Casting gear blanks from scrap aluminium

Post by Harold_V »

Metalman wrote:I am curious and possibly missing something here but if the goal is making change gears from aluminum why cast the metal? Is there no suitable alloy available in plate or billet that could suit the purpose?
Your point is well taken, and can be the correct method, depending on various things. Casting may or may not be suited in your example, although it certainly would work.

For a very revealing experience, try running a Rockwell hardness test on a brass casting. Something that looks perfectly homogeneous can vary all over the map, which is unlike commercially prepared materials, which are rolled to specific sizes. The rolling process has a tendency to create uniform density in the material.

Aluminum can be difficult to cast without inclusions. It must be properly degassed before casting, and not cast to damp environments, where excessive hydrogen can be readily absorbed. Needless to say, such aluminum won't have the properties of rolled aluminum, and if the metal used is unknown, heat treat may be impossible.

All of that being said, having the ability to cast forms that are needed isn't a luxury---it's virtually mandatory, even if you have bottomless pockets and can afford to pay for large sized stock.

I heartily endorse those who have taken enough of an interest to create a small home foundry. For them, the only thing that limits them is the size of the foundry, or their ability to melt all metals. Cast iron and up is difficult with a crucible furnace. For copper, copper alloys and aluminum, they're a perfect fit, and easily built and fired.

Harold
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Ike Turner
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Re: Casting gear blanks from scrap aluminium

Post by Ike Turner »

Metalman wrote:I am curious and possibly missing something here but if the goal is making change gears from aluminum why cast the metal? Is there no suitable alloy available in plate or billet that could suit the purpose?
I had a search online and was unable to find a supplier with plate of suitable alloy in a suitable thickness, so have gone back to the casting idea. I also like the idea of being able to make castings for various jobs and this seems like a worthy first project.
Pipescs wrote: Keep the photos flowing on it.
When I finally make a move on this task, I'll take photos and post them on here. Don't hold your breath though, as I said earlier the place where I may be able to source a crucible is near where I'm working next month, so that will be the earliest I might be able to do something other than ask questions.
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Harold_V
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Re: Casting gear blanks from scrap aluminium

Post by Harold_V »

Pipescs wrote:My thought on their being clay only is based on the below, which is the disruption of the Flasks in the 8 range offered by Budget Casting listing the material used to make them. This is cut an pasted from their website.

#5080 B8 Clay-Graphite Bilge $74.50

#5081 B8 Silicon-Carbide Bilge $157.00

#5082 A8 Clay A $35.50

Having said that, they did come black and went gray after the first firing.
Thanks for this bit of information, Charlie. I must say, I've never seen the designation, so it's new to me. The source I used (Larsen Foundry Supply) sold only graphite/clay or silicon carbide when I was purchasing crucibles. Today was another day of learning for me.

Harold
Wise people talk because they have something to say. Fools talk because they have to say something.
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