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  • ThomasS372 made the instructable General Steps to Sand Casting2 years ago
    General Steps to Sand Casting

    Hello, I'm a master patternmaker and I can answer your questions. The "dirt" you're referring to is indeed, a "sand", but not like normal sand. There are many different types, fineness of granules, etc., how the sand is "bound" together and their selection can be made based on the type of metal that will be poured, the type of surface finish you want on the outside and inside of the casting as examples. Most sand mixtures contain a "binding" agent, along with a very minimal amount of water. (Excess water will turn to steam, creating voids in the casting). Talcum powder is commonly used as a "parting agent" on the patterns to release them from the sand mold. To create a "cavity" within a casting (such as the coolant pathways in ...

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    Hello, I'm a master patternmaker and I can answer your questions. The "dirt" you're referring to is indeed, a "sand", but not like normal sand. There are many different types, fineness of granules, etc., how the sand is "bound" together and their selection can be made based on the type of metal that will be poured, the type of surface finish you want on the outside and inside of the casting as examples. Most sand mixtures contain a "binding" agent, along with a very minimal amount of water. (Excess water will turn to steam, creating voids in the casting). Talcum powder is commonly used as a "parting agent" on the patterns to release them from the sand mold. To create a "cavity" within a casting (such as the coolant pathways in an engine block), requires that a separate, female tool (Called a "Core-box") is made to create the shape of the cavity and register it to the master pattern. This "male" sand shape is called a "Core". To put it simply, the Master Pattern which generally creates the "outside shape", has registrations built onto the pattern (Called Core-prints), that the Core will align with. The drag and cope sides of the sand mold are rammed up against the master pattern. The sand mold halves are separated, the master pattern is removed, the sand "core" made from the core-box is placed into the lower half of the sand mold, aligning it with the "core-print" areas molded within the lower half of the mold. The cope side, or "upper half" of the sand mold is closed over the lower, encapsulating the core inside. After the metal is poured, the sand core is broken loose and out from the casting, creating the desired cavity shape. (See the attached pdf for more details.)

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