Casting sand questions

[mac1911]

I struggle to find answers to my questions with internet searches.

Im trying to figure out how much sand I need fill a mold thats 12x14x 6” deep.
Im also struggling to find casting sand thats sold in quantities that are more affordable
Stuff seems expensive to me?

I depending on cash outlay Im contemplating casting some aluminum and bronze parts.

 

[matthewsx]

LxWxD?

12 cubed is one cubic foot, so depending on your mold you could possibly get away with half a cubic foot.

I’m no expert in casting, haven’t done it since Jr. High. Might be some homebrew formulas out there, or maybe there’s somebody close to you who would be willing to share.

John

 

[GeneT45]

Do yourself a favor and make your own green sand (sand of appropriate fineness + fireclay). It's much nicer to work with, cheaper and easier to retemper, and doesn't stink like oil-tempered sands. I'm sure I can find the formulation I used if you need it. As to how much, I'm too lazy to figure it out, but if you're making your own it's so cheap you won't care.

GsT

 

[ChazzC]

I struggle to find answers to my questions with internet searches.

Im trying to figure out how much sand I need fill a mold thats 12x14x 6” deep.
Im also struggling to find casting sand thats sold in quantities that are more affordable
Stuff seems expensive to me?

I depending on cash outlay Im contemplating casting some aluminum and bronze parts.

Spent foundry sand was all I could find data for: 160 lbs./cu.ft.; x 12x24x6/1,728 = 93 lbs. Spent sand may be denser than fresh, but I don’t know.

 

[benmychree]

I always used Petrobond (oil) sand, the usual quantity is one sack, about 80 lbs, I think, this situation is one of "the more the better" as there is attrition as sand next to the casting gets the oil burnt out of it and should be discarded as with use, if it is simply allowed to mix with the unburnt sand, it lessens the bond a little at a time until the whole heap is near useless, Oil sand needs no tempering, and if castings are allowed to cool in the mold, personally, I am not bothered by the smoke smell. Unless one has a muller, it will not work very well to try to make your own green sand just adding clay to sand and mixing it does not create the best bond. Fireclay is not what is generally used to bond sand. Here is a site I found online that sells premix green sand.

Green Sand Metal Casting Premix - 30 lbs.

Metal Casting Green Sand Greensand Metalcasting Bentonite Premix Metal Working

www.qualitytargets.com

 

[benmychree]

I finally remembered! The clay generally used is Bentonite. The fireclay that I have seen contained a lot of large particles, something no wanted in molding sand. This is fine for aluminum and brass/bronze, for iron, other ingredients are used, notably finely ground coal to prevent the sand being fused (burned) onto the castings.

 

[benmychree]

Bronze is not an easy metal to cast, the molten metal tends to take up gasses from the furnace atmosphere, causing porosity in the castings, it needs a oxidizing flux in melting, followed by a degasser, in the form of a copper jacket filled with phosphor tin shot, which is plunged
into the melt before pouring. Aluminum also can have porosity problems, using die cast aluminum such as pistons can create problems in casting, that alloy for die casting contains iron to prevent the metal from sticking to steel molds, it has the effect of narrowing the solidification temperature range' you have to raise the pouring temperature to avoid having the metal solidify too soon and not completely filling the mold, so you have to raise the pouring temp. resulting in excessive shrinkage and casting defects. Making patterns with uniform cross sections helps, but that is not always possible.

 

[o0norton0o]

Notice how this guy puts his left foot on the mold when he pours the molten aluminum. I'm thinking that he used to do that with his right foot previously... I get the feeling that does this a lot and has his process down pat. He makes it look simple...

 

[GeneT45]

I finally remembered! The clay generally used is Bentonite. The fireclay that I have seen contained a lot of large particles, something no wanted in molding sand. This is fine for aluminum and brass/bronze, for iron, other ingredients are used, notably finely ground coal to prevent the sand being fused (burned) onto the castings.

You're correct - I wrote fireclay, but should have said bentonite - my poor recollection.

You can temper Petrobond with oil that the same company sells for the purpose (so you don't have to discard the blackened portion adjacent the casting) or with Peanut oil. If you don't, your PB degrades a little each time as even the non-blackened parts dry some and the whole mix bonds a little less well. You can 'mull' green sand on the floor, with your feet and a shovel and it will work every bit as well as Petrobond - except that there is no smell and it's easier to maintain.

GsT

 

[Smithdoor]

I struggle to find answers to my questions with internet searches.

Im trying to figure out how much sand I need fill a mold thats 12x14x 6” deep.
Im also struggling to find casting sand thats sold in quantities that are more affordable
Stuff seems expensive to me?

I depending on cash outlay Im contemplating casting some aluminum and bronze parts.

It takes about 70 pounds of sand.
Natural bond is good sand . The oil boned sand is great but costly.

Dave