Casting AL molding box

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vtsteam:
Andrew, great, thank you -- that's a great help! :bow:

And mike found it: http://madmodder.net/index.php/topic,3545 -- will give that a read! :beer:

(note, to link just go to the page you want to link to and highlight and copy what is in the top of you browser for an address. Then go to the post you want to put the link into, and paste it right in. -- hope that helps.)

And since it's raining today and no casting, I've been trying to find the thing about "green oak stick" for stirring. Can't find anything. So nobody try it, for safety sake.

I did find stirring the melt with a pine stick (presumably dry) in Gingery's Charcoal furnace book -- (for aluminum) -- he says it is supposed to improve the melt, but he didn't notice any difference. Also B.Terry Aspin in The Backyard Foundry p. 85 shows a wooden rake for skimming the melt (iron) -- he says oak and beech are suitable -- (presumably dry). I don't know where that memory of "green oak stick" comes from. So best ignored.

But re-opening Aspin's book brought back all of the excitement of first reading it, and the wealth of information in this little book, wonderfully illustrated. Great drawings of pattern making, core boxes, coring, for steam and workshop tool making. And coincidentally, making flasks -- including many different types of construction -- sheet metal, cast, and what really surprised me, concrete.

Now I'm not interested in making concrete flasks. But I'm wondering about the cover plates anew. Seems like there are mixed opinions about concrete spalling and splattering grit and molten metal all over the place when hit with hot iron.

I'm thinking the reason for the mixed reviews is differences in concrete mixes, bubbles and moisture content of the concrete itself, rather than everybody arguing right and wrong from a firm standpoint.

Concrete can absorb water if mixed in some proportions, and is pretty impervious in others. In fact Portland cement, mixed neat is waterproof -- and is used in waterproofing tanks and swimming pools. So I'm wondering about this -- I always get curious about this kind of stuff -- especially when there are big disagreements by believable people on both sides of a debate -- I often wonder, maybe they're both right, but not talking about the same thing.

If concrete plates could be used for pouring (and if of the right mix and kept dry indoors) they would seem like a very good, nicely massive, inexpensive cover plate material.

awemawson:
At my last place I had a purpose built 'fireproof' building about 20' x 15' for casting - the floor was concrete and the furnace was in a pit at one end. The apex of the roof was a 10"x6" steel beam that I had a runner on with a block and tackle for the heavier stuff.

All my pours were on that concrete floor. I just laid out my copes & drags in a line on their boards, and if I was being particularly keen I'd sprinkle moulding sand between the flasks, and either side, but usually I didn't. The damage to the boards was not much to be honest - ok they'd burst into flames and smell awful, but knock the dribbles off and a handful of sand and when the smoke had cleared it was fine !

Worst time was when I had a 'helper' who insisted on chatting and not concentrating, and managed to drop a crucible of bronze. Oh boy did that go EVERYWHERE ! I have a ceramic chip forge, which stands on a heavy bent sheet steel base, and it ran under it in a thin puddle gluing it to the floor! Luckily I insist on proper foundry boots with fireproof soles so we were ok. Never did ask him to 'help' again :)

vtsteam:
Sounds like the "spalling" explosion of concrete and metal -- often warned about -- didn't occur though -- or did it?

If it was done right, a 9x 12" cover plate probably couldn't hold a signifigant amount of spilled metal at all -- ironman uses a half circle cutout above the sprue in the plate, and those edges could be beveled as well.

Or if the top cover plate was slightly convex or even flat sloped toward the sprue pouring hole, seems like there would be not much chance of any spilled metal staying on it.

awemawson:
Here you are Steve, don't bother making flasks, borrow some of these (I bought the contents of a foundry that went to the wall some years back):

vtsteam:
I'm going to have to build a boat to get em! Nice, though.

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