You need some kind of molding process in order to make a casting. The size of the casting determines the appropriate process. Those processes require different kinds of pattern equipment.
This casting is made in a process called “air-set”, where sand is combined with a chemical binder and packed into a set of mold boxes that contain the pattern. The binder reacts and causes the sand to harden, the molds are removed from the boxes, fit together face to face and clamped tightly together. The mold is filled with molten metal and allowed to solidify. The mold is broken open and the casting is removed.
This is the casting we want to make.
Mold boxes are not just wood tubs, they are built so that the shape of their bottom face form a means of accurately “matching” both halves of the mold together.
Look closely at the cross section of the bottom faces of the boxes. One mold is constructed to form a pocket on its face; the other mold box is constructed to form a raised pad on its face.
I’ll let the images speak for themselves.
However, I’d be happy to clarify what is going on in a picture if anyone had a question.
Unfortunately It’s another sad story about a declining trade.
This was awesome wood pattern making work before the machines took it over. I’ve built patterns like this both ways and I’ll take my shop apron over my keyboard…anytime.