plate miscasting (was "Fixing Plates")

[centipod at mac.com]

thanks, Frank - I can picture it very clearly now.

Allen
On 9 Feb 2007, at 13:43, Frank Emerson wrote:

> >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


Allen Wright
6 Clay Court, 219 Long Lane
London SE1 4PB
United Kingdom
020 7378 8265
0780-688-1325 (mobile)




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