Subject: Re: core making for sand casting

From: [email-masked]
Date: 2 Nov 1995 05:29:35 GMT

>   [email-masked] (Rick Cook) writes:
>  Scott Riddles wrote:
>  >Does anyone have information about making cores for sand casting?
>  
>  Once again, Lindsay Publications has a book about this. Address in the FAQ.
>  
>  --RC
>  
>>>>
Actually, they have ten or twenty. If I were to only buy one, It would be one of those 
by C.W. Ammen. His Casting Brass covers a range of brasses and bronzes. Casting 
Aluminum covers (surprise) aluminum. Topics include properties of various alloys, sand 
mixtures, core information, general information on types of furnaces, etc. His books 
don't assume that you have a foundry supply store next door and have lots of common 
sense information for the amatuer.

Dick

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From: [email-masked] (Bruce Holder)
Date: Thu, 2 Nov 1995 17:22:20 GMT

Rick Cook ([email-masked]) wrote:
: Scott Riddles wrote:
: >Does anyone have information about making cores for sand casting?

: Once again, Lindsay Publications has a book about this. Address in the FAQ.

  The U.S. Navy Foundry manual (1958, I think) has a chapter on making
cores. It seemed pretty informative to my untrained eye. This book is
also available from Lindsay and I have also seen it at technical book
stores.

Bruce

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From: [email-masked] (DAVE BOZARTH)
Date: Thu, 02 Nov 95 22:30:00 -0800

SR>Does anyone have information about making cores for sand casting?

David Gingery discusses core making in his book THE METAL LATHE.
He uses a mixture of 20 parts sand to one part wheat flour tempered with
1 part molasses in 10 parts water. The core is formed in a wooden split
mold. One half of the wooden mold is used as a pattern to cast an
aluminum core plate to support the core when baking it.
---
 þ OLX 2.1 TD þ Chicken heads are the chief food of captive alligators.

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From: [email-masked] ()
Date: 3 Nov 1995 03:45:38 GMT

BrnzCaster ([email-masked]) wrote:
: In article <[email-masked]>, [email-masked] (Scott Riddles)
: writes:

: >Does anyone have information about making cores for sand casting?
: >I am trying to pour a thin walled casting. The Petrobond sand 
: >cores I have been making need additional strength.  I have seen the
: >processes of making shell cores, baked cores, and air-set done in 
: >foundrys but cannot find a good source of detailed information.
: >
: >

Even easier (maybe cheaper too) just ask your local druggist or chemical
suplier for water glass - the common name for sodium silicate. I used a lot
of it for making very complex and fragile cores for bronze casting. Mixed
sand and water glass in a Hobart resturant mixer, put mix in core box, gas
with co2 and voila - a strong core.

: I use Chem-Bond #12 as the bonding agent for my sandcasting cores. It is a
: sodium silicate based material and is activated immediately with CO2 gas.
: You can make some very fast and stable cores with this method. I use 250cc
: of Chem-Bond to each gallon of silica sand (120 GFN) and gas with CO2 for
: about 10 seconds on small cores.
: A supplier of the Chem-Bond in "hobby sizes" (quarts) is the following
: mailorder company...
: Power Model Supply Co.
: 13260 Summit Drive
: De Soto, MO  63020
: 1-314-586-6466

: You can vary the hardness of the cores by changing the grain size of the
: sand and the ratio of Chem-Bond used. Perpared cores have a shelf life of
: a couple months. Make sure you use good core venting practices, as there
: is considerable off-gassing of the core during pours.
: The Chem-Bond wetted sand has a shelf life of several months if you keep
: it in a TIGHTLY sealed plastic container. Any exposure to carbon dioxide
: will harden the sand.

: Winston

: *******
: Winston W. Harness, Metalsmith
: [email-masked]
: [email-masked]
: http://www.mmf.com/metal/home/wwh/

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From: [email-masked] (BrnzCaster)
Date: 4 Nov 1995 02:17:45 -0500

In article <[email-masked]>, [email-masked] ()

>with co2 and voila - a strong core.

Yes, you can use the pure sodium silicate solution to make cores, but
there is also a down-side.
The commercial preparations such as Chem-Bond also have additives (sugar,
etc) that control the hot crush strength of the cores. Using pure sodium
silicate usually produces a very hard core that doesn't collapse during
casting solidification and are sometimes very hard to remove. You run the
risk of cracked castings with very hard cores (depending on the alloy used
and the pattern design).
You can also add other things yourself to tune the core characteristics;
try things like bentonite clay powder, iron oxide powder, sugar, various
flours, etc.
For most of my work, I stick with the straight Chem-Bond #12 and silica
sand; I control the core characteristics (crush and surface finish) by
using different grades of sand and different mix ratios.
It has been a couple years since I bought Chem-Bond in bulk but I think
the last I got was about $65 for 5 gallons.

Winston

*******
Winston W. Harness, Metalsmith
[email-masked]
[email-masked]
http://www.mmf.com/metal/home/wwh/