Making a solid rectangular cube casting is pretty straight forward. We simply place the solid cube face down on the mold board, shake on some parting dust, riddle some sand over the rectangular pattern, and ram the sand. Next, turn over the drag, attach the cope to the drag and repeat the process. Removing the cope, we lightly tap the pattern and lift it out of the drag. Add some sprue and vent holes and we're ready to pour our casting.
In order to overcome this problem, we have to modify the pattern.
The SAND CORE is made in a specially prepared CORE MOLD that resembles the shape of the hole slot, etc that we want to create. The CORE MOLD is filled with a sand and glue mixture, baked to form a solid mass, and then inserted into the larger MOLD.
If we place our two sand cores together - the cylindrical sand core and the V-shaped sand core - we thus create a hole through the middle of our rectangular casting.