Good sources for learning basics/My basic Questions

[coolhotdogguy]

So I saw a YouTube video and decided I wanna try this metal working stuff out a bit. I have a bunch of questions and was wondering what are some good sources to check out to make sure I do this right and safe?
Guess I'll also ask my questions here!

1. I'm thinking of casting aluminum and I would like to use old soda cans. Will this ruin a clay graphite crucibal?
   
   
2. Any ideas where to find excess aluminum for melting?
   
   
3. Can I temper my crucible in a propane forge like in the video?
   
   
4. How important is borax in getting my clay graphite crucible ready?
   
   
5. I have a clay graphite crucible and a silicon carbide graphite one. What temperatures can they handle? What is the difference?
   
   
6. Are sand molds a good place for a beginner to start? Any tips?
   
   
7. What are good ways to finish an aluminum mold? Polish? Sandpaper?
   

[rleete]

Probably the best place to get info on casting would be https://www.backyardmetalcasting.com/ Plenty there to read, and most likely your questions would be answered just by reading.

1. Not really a viable source of aluminum, as you will find out on the site above. Takes WAY more cans to get usable metal than you would think. No idea about the crucible.

2. Old screen doors were the easiest for me to get. Roadside pickup around garbage day can yield good materials. Otherwise, contact a local metal recycler. They will sell you anything you want at per pound pricing, usually just pennies above spot price.

3. - 7. No idea, see site above for good, easy to understand info.

[Dr Stan]

I'm thinking of casting aluminum and I would like to use old soda cans. Will this ruin a clay graphite crucibal?

No, but as rleete said not a good source.

Any ideas where to find excess aluminum for melting?

Engine rebuilders. Pistons and connecting rods are high grade aluminum and small enough to fit in the crucible. You don't need to clean them up, just make sure to use enough flux. The piston rings can be removed with a bent piece of O/A welding rod. A small engine rebuilder is also good, but you have to break up the engine blocks and the quantity is usually not as high.

Can I temper my crucible in a propane forge like in the video?

Yes

How important is borax in getting my clay graphite crucible ready?

Very

I have a clay graphite crucible and a silicon carbide graphite one. What temperatures can they handle? What is the difference?

Been awhile since I looked this up. You should be able to find an answer on-line.

Are sand molds a good place for a beginner to start? Any tips?

Yes. Use water based casting sand. Much easier to temper. Put your molds on a piece a sacrificial plywood or OSB, NOT on concrete. Water expansion ratio to steam is 1600 to 1. Concrete is full of water. Think about it.

What are good ways to finish an aluminum mold? Polish? Sandpaper?

Do you mean a pattern? Either will work, but for sand casting the draft on the pattern is more important than the finish.

Be careful, very careful. A good pouring temp is around 1250 degrees F. Plenty hot enough to burn the crap out of you.

If you can still find a copy of the US Navy's Foundryman manual, buy it. Probably the most definitive reference for foundry work ever written.

[Dr Stan]

https://www.amazon.com/Foundry-Manual-Un...1410109003

Here's a source for the Foundryman's Manual.

[Hawkeye]

As the guys have said, beverage cans aren't the greatest source of aluminum. Generally speaking, the best source of metal for a given task is to use an item that was made the same way. For casting aluminum, melt down something that was originally cast. That metal will have the right added metals (such as zinc, etc.) to cast well. I started out melting down aluminum electrical cable, which is pure aluminum. Really nasty to machine.

I've had success with wooden patterns forming green sand, as Stan mentioned. I even made a replacement handwheel for my bandsaw by using the broken plastic wheel as the pattern. Another method that's worked for me is Lost Foam Casting - you carve the pattern out of insulting foam and coat it in drywall plaster. After it dries completely, you can sink it into a bucket of sand, using a controlled flow of air to liquify the sand. When you pour the molten metal into it, the foam burns out and is replaced by the aluminum. Do it outdoor, with a bit of a breeze (or a fan) to blow the chemical smoke away. Search Lost Foam Casting. There is plenty of information out there.

And take Stan's advice seriously. Plan for the what if's. Leather boots, heavy gloves, no synthetics, face and eye protection.

[Dr Stan]

Excellent point about Lost Foam Casting.  I have made patterns out of foam to make aluminum patterns.  Just make sure you compensate for the shrinking of the casting that occurs during cooling.  In general that is 1/8" per foot.  

Take Hawkeye's advice about the fumes from foam.  If you ever get a whiff of it you'll make sure you never do so again.  Make yourself a hot knife to cut the foam.  It can be used indoors as it does not produce much in the way of fumes.  I like the idea of coating it with plaster.  I used diluted wood glue in the past and it required several coats.

If you use a broken plastic part for a pattern in general it is a good idea.  One word of caution, make 100% sure it is NOT PVC.  The fumes from PVC are extremely toxic.

Consider buying a pattern maker's scale from Travers, McMaster, Grainger, or a foundry supply company.  For a foundry supply company find one that caters to artists/sculpture casting. They will provide consumables in sizes that are appropriate for the backyard foundry.  There was one in Tulsa OK I used in the past, just cannot remember the name.  Paxton Patterson still supplies school foundry's, but tends to be pricey and does not carry nearly as much as it did in the past.  One can find mason's trowels that will substitute quite well.  A foundryman's spoon is fairly easy to make.  Ditto for a riddle.  I used a 5 gallon bucket to make a riddle.  Cut it down to 4 or 5 inches tall and cut most of the center out of the lid.  Sandwiched some fiberglass screen between the two pieces and had a nice riddle.

A foundry flask is also very easy to make.  Look on YouTube for examples.

You guys got me Jones'n to build another foundry.  As if I already didn't have enough projects to tackle.  I need to post more pics of my car lift project and the big honking hole in the floor of my shop.

[Highpower]

(09-28-2020, 10:19 PM)Hawkeye Wrote: And take Stan's advice seriously. Plan for the what if's. Leather boots, heavy gloves, no synthetics, face and eye protection.

(09-28-2020, 05:40 PM)Dr Stan Wrote: Be careful, very careful.  A good pouring temp is around 1250 degrees F.  Plenty hot enough to burn the crap out of you.

I went out to the storage shed at my previous house one day to do some lead smelting. After I was half-way through getting everything set up I realized I was still wearing a pair of athletic shoes. I didn't want to shut everything down to go back to the house and I told myself - "Well, I'll just be really careful. "The ONE time I had a mishap - was the ONE time I got lazy and didn't change into a pair of leather boots.

The top of my right foot got doused with a stream of molten lead at a mere 800° F and I couldn't get that shoe off fast enough. Had it been molten aluminum I would be missing a lot of toes right now. Hard way to learn, but brother I did LEARN. Like Mike said... "Plan for the what if's?" Before you make a move, ask yourself a question. "If I do this - and something unexpected goes wrong - how bad am I going to get hurt?"

[Dr Stan]

I had an uncle who worked at a steel mill in Youngstown, OH. They wore thermal underwear year round to help keep cool. He was working as a furnace inspector and standing nest to an open inspection hatch the size of a man door when there was an explosion inside the furnace. Unfortunately for him he was wearing polyester thermal underwear. He caught on fire and was burnt 50% 2nd degree and 50% 3rd degree. By all rights he should have died, but lived. Multiple months and surgeries he finally was discharged from the hospital looking like a patchwork quilt from all the skin grafts. His survival was so far off the chart his case was written up and published in the New England Journal of Medicine.

Yes aluminum pours at about one-half the temp of steel. but as we have been saying take safety precautions very seriously.

The worst incident I had teaching foundry was when a student accidentally added some magnesium scrap to a hot crucible. It set off a Class 4 fire (metal fire) and it looked like a large Roman candle coming out of the furnace. I suited up, grabbed a one man shank and took the crucible outside so it could burn out.

None of this prevented me from foundry work. I find it quite enjoyable even with the risks taken.

[Hawkeye]

I should point out that the broken plastic handwheel wasn't burned out of the mold. I used it as a pattern in a green sand mold, just as a test. It worked so well, I machined the thing and put it on the saw. Still using it.

[Dr Stan]

That's what I thought you had done.