Oil-Bonded Green Sand Recipe?

[Vrogy]

A friend and I have been messing around with metal casting for about 2-3 weeks now, and we can't get it to work well, beyond the lost foam process, which is easy. We've mixed up about 3-4 different formulas, with different oils and different sands, and we keep getting sand that just falls out of the cope.

We've tried sifting sand down into fine dust with grease guard meshes, that helped a little. Also tried was grinding kitty litter down into powdery bentonite clay- that helped a lot. So far, though, either our cope falls out when parting, or the sand catches fire when pouring and the metal solidifies in the sprue.

I get the feeling that our sand is to blame. Is there a concise, thoroughly-documented formula for oil-bonded green sand for the DIYer?

[pointcloud]

Use a little more Bentonite, it will not burn out until around 3500 deg.F

The oils are causeing a big problem... change it to water... It will hold ok with the bentonite...

Oil burns and has to exhaust, causing the metal to cool with the exhaust of the oil fire...

[beone]

OK, as a home founder for about 25 years I am going to chastize you just a bit.
First off you can't have oil bonded green sand. No such thing. you may have green sand ( which I use) which is sand clay and water, or you may have oil bonded sand which consists of sand, aspecially modified type of bentonite clay normally refered to as Bentone, oil and a catalyst. DO SOME RESEARCH!! Get Gingerys book 'The Charcoal Foundry', get Bill Ammens books. Both will tell you how to make green sand, not hard, just a lot of hard work. Probably the biggest help to make your sand better is to mull it. Think of Kneading bread-over and over and over. In general the more you work the sand the better it is. When I haven't used my sand in a while it takes a while for it to work well. Each day I use it it gets better. Oil bonded sand needs an even more agressive mulling.
A good formula for green sand is 100 lbs fine sand, 10 lbs bentonite, 10 lbs water. I lake to add some organic stuff to help hold the water so I ususlly add 1/2 lb of wheat paste. Mix. Mix, Mix. Mix some more. pack it break it up. Work it over and over. Green sand can make just about any casting you can think of.
Dave

[pointcloud]

This link says that bentone is a lubricant and has greases in it.. Which I am sure would make lots of gases..

http://tds.econocophillips.com/catal...tone%20TDS.pdf

[Kipper]

Nice choice of a hobby Does the sand hold shape when a handful is squeezed? and what are your flasks like? Pictures would be nice. If you're using large flasks try and incorporate some supports for the sand. Could you buy some oil bonded locally? It's slightly more expensive than green sand and comes in facing and backing grades... I gave up using green sand around 10 years ago as the amount of use I gave it made it hard work.

[Vrogy]

Here's the flask we're using:


We actually got our sand to hold in today- we just mixed up more, again, but with water instead of oil.
We cast a nice little aluminum shot-put ball.

I'll probably be back, complaining about sand again, but for now switching to water helped. Thanks to everyone who helped.

[pointcloud]

Great!!! Would love to see a good part...

[metalworkz]

Hi Vrogy,
I use the Petrobond oil bonded sand with great results. You can get many pours from one 100lb canister of the Petrobond and it can be re-mulled with the oil binder to be used again. You may need to construct a muller to remix it but it should not be too difficult and your molding and casting problems may disappear in the process. The sand is very fine grain and you can achieve very good definition in your castings with this sand with regular sand molding techniques. I am not sure but I think I paid $75 for 100lbs, but it has been a while since I bought it so prices will be different now.
Regards,
Wes

[Vrogy]

Wes, what's the volume of 100 pounds of compacted petrobond?
About how much is that in terms of actual filled flask volume?

I didn't think petrobond was so cheap, nor available where I am.. but if it is, and maintenance costs aren't prohibitive, it may indeed be the way to go, and worth a trip to a dealer.

[metalworkz]

Hi Vrogy,
The 100lb container for the Petrobond is roughly 11" round by about 24" high. I am offering these dimensions as an estimate of the actual volume,
and this is not in a fully packed state either.
Wes

[rickharris]

Try:
* 100 lb. of very fine silica sand (100 to 150 GFN)
* 6 - 7 lb. of Bentone (cheapest you can find)
* 3 lb. of Indopol L-100 oil
* 0.10 to 0.20 lb. of Propylene Carbonate (or Methanol or Isopropanol)

from:

http://www3.telus.net/public/aschoepp/sand.html

Note what they say about petrobond

[skzzyx]

Hi all! new guy to this forum. been casting metal for about 25 years mostly hobby made a little money! my question is where on earth do i get bentone? i live in bend oregon usa.