plate miscasting (was "Fixing Plates")

[Frank Emerson]

>So if I'm understanding this correctly, the top half of the pattern, or cope, would have had to have been refashioned (or at least the part in >the triangle) once they had discovered the error?

Not exactly.  The pattern, from which the cope and drag are made must be modified.  The cope and drag constitute a one-time temporary mold to make one casting.  The shrinking of the plate as it cools pretty much wastes it for any further use.  After the casting has cooled enough to be removed, the cope and drag are nothing more than a pile of black sand, and the wood and wire framework to start over again making a new cope and drag from the pattern for the next casting.  

There are more efficient methods for high volume production situations, but this is the basic sand casting method.  The much-touted vacuum-form process is nothing more than lining the cope and drag with a thin plastic film, which vaporizes as soon as the molten iron contacts it, but it provides enough of a barrier  between the iron and sand to produce a smoother surface that will require less filler to make the finished plate surface smooth.

Frank Emerson
pianoguru at earthlink.net
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