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Cutting Sprues and Gates in the Cope

The hole into which the melted metal is poured is called the 'sprue'. You can buy sprue cutters but I usually use a
piece of sink drain pipe widely available at hardware stores. In this case I am cutting 2 sprue holes. This is a little
unusual. In essence, I am making 2 separate molds in the flask (that's what the aluminum molding container is called).
The black mark on the cutter is a depth guide. I only need to punch a hole to the level of the top of the drag.

I use a small flat blade to cut a shallow funnel around the top of each sprue. This will help get metal into the hole and
minimize spilling.

I use my fingers and thumb to press and smooth the sand around the top of the sprue. You don't want any loose sand
to fall into mold when the metal is poured.

 

Here the sprues and cut and cleaned.

Before opening the mold, I use the rubber mallet to tap around the edge of the flask lightly. This helps the patterns and 
the two halves to separate cleanly.

In this photo, the cope has been lifted off and set aside to reveal the patterns in the drag. The brown sand is left over 
from cutting and trimming the sprues.

Here is the cope which has been set on one side. The sprue holes are on top, the mold of the finial patterns below.

I use a melon baller to trim the loose, rough edge of the bottom of the sprue. Again, It is important to keep all loose
sand out of the mold.

I used a plywood board to support the sand and rolled the cope over allow me to work on cutting channels from the
sprue holes to the patterns. The channels are called gates.

I use a small piece of folded sheet metal and a flat blade to cut the gates. The gates are cut just into the pattern close
enough to allow metal to flow into the mold but not so close as to crumble the edge. This is a difficult project - most
molds/patterns have a larger area into which gates can be cut. In this case, this is the only way I could gate the mold.

I'm going to gate both the cope and the drag. Time to move on to the drag.

 

<Next Page> Gating the Drag


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