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?

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[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.

[rickharris]

I guess your referring to Bentonite - a kind of clay used to make up casting sand formulae.

One source is Kitty litter - Bentonite is a main constituent of this useful material in the workshop.

Useful, because by it's very nature, it absorbs spills like a sponge.

Some details http://www.steetley.com/ here

[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.

Thanks for the reply- have access to regular benonite as i live in a farm area where they line ponds with it-but i read that bentone was a form that absorbed oil rather than water.

[beone]

No, bentone is a specially modified bentonite so it absorbs oil properly. one use is by well drillers to make drillers mud.

[rickharris]

Hi, The following is extracted from Wikipedia

"The ionic surface of bentonite has a useful property in making a sticky coating on sand grains. When a small proportion of finely ground bentonite clay is added to hard sand and wetted, the clay binds the sand particles into a moldable aggregate known as green sand used for making molds in sand casting. Some river deltas naturally deposit just such a blend of such clay silt and sand, creating a natural source of excellent molding sand that was critical to ancient metalworking technology. Modern chemical processes to modify the ionic surface of bentonite greatly intensify this stickiness, resulting in remarkably dough-like yet strong casting sand mixes that stand up to molten metal temperatures.

The same effluvial deposition of bentonite clay onto beaches accounts for the variety of plasticity of sand from place to place for building sand castles. Beach sand consisting of only silica and shell grains does not mold well compared to grains coated with bentonite clay. This is why some beaches are so much better for building sand castles than others."

Although I didn't look for a specific formula =- this is an extract from Conocos deffinition of Bentone

"Bentone is high-quality, non-soap, extreme-pressure, clay-based
grease developed for lubricating industrial bearings and
machinery operating under heavy loads and subjected to high
temperatures.
Bentone, unlike conventional soap-based greases, has excellent
storage stability and retains its consistency at high temperatures.
In addition, it adheres to the surface to which it is applied and
has excellent water-washout characteristics.
Applications
Bentone is recommended for medium-to-large low-speed bear-
ings commonly found in rolling and strip mills, Banbury mixers,
jaw crushers, kiln cars, drying ovens, steel mills, aluminum,
glass, rubber and cement plants where conventional soap-thick-
ened greases normally fail due to the extreme high temperatures
encountered. Frequent relubrication intervals are recommended
under these conditions to minimize bearing failure due to lack of
lubrication.
Bentone is formulated with high-viscosity index paraffinic base
oils and fortified with bentonite clay thickener and anti-wear
additives to provide exceptional protection for the bearings and
moving parts when subjected to high operating temperatures."

[RBrandes]

I started with green sand in high school in the '60's, but after trying petrobond I was sold on oil bonded sand.
It can sit for years and still be ready to go where as green sand will dry out, need to be tempered and sit overnight for best results. I am a spontaneous guy and don't like to wait!

Look here for the K-Bond formula, developed at Kent State, OH with materials, alternate materials and sources. We have determined that K-Bond is basically the same as petrobond.
http://www.foundry.ray-vin.com/k-bond/k-bond.htm

Other foundry stuff at:
http://www.foundry.ray-vin.com/

Regards, Ray in FLA

[Vrogy]

I started with green sand in high school in the '60's, but after trying petrobond I was sold on oil bonded sand.
It can sit for years and still be ready to go where as green sand will dry out, need to be tempered and sit overnight for best results. I am a spontaneous guy and don't like to wait!

Look here for the K-Bond formula, developed at Kent State, OH with materials, alternate materials and sources. We have determined that K-Bond is basically the same as petrobond.
http://www.foundry.ray-vin.com/k-bond/k-bond.htm

Other foundry stuff at:
http://www.foundry.ray-vin.com/

Regards, Ray in FLA

Wow. I'm glad I revisit old threads. Awesome stuff, thanks!

[spencer313]

See also: http://www.foundry.ray-vin.com/k-bond/k-bond.htm

[makarovowner]

Hello, I have a few questions about green sand also. I contacted masons supply about silica sand and it is no longer available. They suggested to me dolomite sand as a substitution. Have any of you used dolomite? If so how did it work out for you? Also is bentonite clay the same as fireclay? I have seen both mentioned as I study forums on green sand. One last question. What is the best molding process for parts with inner and outer dimension duplication needed as a one piece end product? Most of the processes I have seen only concetrate on outer dimension. I am a newbee, experianced carpenter and woodworker, very mechanical, but not a machinest. I find the whole home foundry process fascinateing and opens shop options to levels I never considered. Thanks alot guys.