Thursday, April 8, 2010

Mold Board Basics - The Follow Board

In some cases, the parting line of the pattern will not be a surface that is even and parallel across the cope and the drag but may protrude above a "normal" flat-surface parting line.  And we may also not be able to fabricate a "split pattern" in the usual two halves.
This presents a problem when we place the pattern face-down on the drag.  In order to overcome this problem, we build a special mold board for this pattern that conforms to the outline of the pattern so that most of the parting line will rest flush with the mold board.  This special mold board with a cavity or socket in it and which conforms to the form of the pattern and defines the parting surface of the drag is called a "FOLLOW BOARD".  The pattern rests on the FOLLOW BOARD while making up the drag half of the mold and, in so doing, establishes the correct parting line.

When the drag (or in this case, the FOLLOW BOARD) is flipped over to make the cope part of the mold, the FOLLOW BOARD is removed exposing that part of the pattern that will be incorporated into the cope.  The green sand can then be formed about this protrusion so as to make a clear parting line between the cope and the drag.

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