Home foundry metal casting

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bcgold
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Home foundry metal casting

Post by bcgold »

It all starter with a lapidary hobby, I wanted a flat lap. After examining one I had borrowed and seen how ridiculously simple it was decided to make my own.

Purchased a silicone carbide crucible some sand, piled a few bricks together for a furnace and fired it with a tiger torch to melt the scrap aluminum pistons.

Used the aluminum pan from the borrowed lap for my pattern, in less than an hour had a brand new pan plus the motor mount that also housed the eccentric that gave the whole thing vibratory motion. Cit the sprues off then cleaned up the cut area.

That first casting was over 4o years ago but nver forgot the thrill of having made something useful from scrap aluminum pistons.

Then about eight years ago built a large furnace from a castable refractory that was propane fired, used an old roofers tar kettle torch that put out a large amount of BTU';s.

The kettle torch uses liquid propane that is turned into a vapor at the head, the advantage here is that your bottles wont freeze up. You can run them completely empty.

The sand of choice is an oil based sand the sand is olivine based and is fine enough to pick up a fingerprint should to wish to cast one. This sand picks up the finest detail then being oil based any dummy can be a pro with out worrying about a steam explosion.

I have not cast anything for the past couple of years now but when I did was making fishing weight and scuba weight molds along with the Case tractor company's mascot Old Abe fence finials. All of which sold on flebay.

Often the second chance offers kept me at the furnace into the wee hours of the morning.

Pattern making or copying some of the things used, wood, modelers clay, RTV compounds from Shore and old pressure cooker to remove air bubbles from your RTV compound before pouring. Bubbles are removed with vacuum or by pressuring the pot to squeeze them down small. I prefer using vacuum.

No longer have the large furnace but have a 15KVA induction furnace that will do five pound melts and is capable of doing stainless steel, brass and copper.

With the lost wax method you can make decent castings.
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contrahead
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Re: Home foundry metal casting

Post by contrahead »

You could use some pictures to aid your discussion. A lot of that industrial / metallurgy slang flew right over my head. You need to keep the conversation simpler for simpeltons like me.

I had no idea what a “flat lap” was until today when I queried the term.

Am I right in assuming that RTV = (Room-Temperature-Vulcanizing silicone)? Are you casting hot metals into silicone molds or are you only casting resin in RTV? Your subjects jump to induction furnaces and then to investment casting (lost wax); terms I've heard, but know little about personally.

It seems like you've lumped many detailed subjects together, and need to spread them out some. For example: I'd like to know more about induction furnaces. I found this currious video while trying to figure out what an induction furnace was.

Give some pictures. What does your induction furnace look like and how is it used?
Omnia mea mecum porto
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contrahead
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Re: Home foundry metal casting

Post by contrahead »

A while back I made a crucible furnace and even have a few pictures to prove it. Air is forced in by a portable hairdryer. I cast it in refractory (a mix of equal parts – sand, fire clay, portland and perlite.
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My little furnace easily melts pennies (which are all zinc) but was a flop for melting copper and cartridge brass; for a couple of reasons. The internal volume was too small to hold enough charcoal to reach proper heat. Barbecue charcoal is a poor fuel. The furnace lacks a proper crucible, but instead uses a steel one that I welded up, which flakes off and contaminates my sample metal. I might have used a propane weed burner/ torch but put that off for the future. I favor the idea of creating a pressurized reservoir and drip line to drop waste oil into the air-stream (as fuel). I got distracted and have not done that yet.

Still, as it is it makes a fine furnace for charcoaling my version of “oaking sticks”. I tie up a wad of dried, hardwood tree limbs (bottle mouth diameter or less and cut bottle length), place it inside and set it on fire. Use the hairdryer to speed the burning to my desired char, then smother the furnace with wet rags to choke the furnace tight and let it sit overnight.
Omnia mea mecum porto
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