Foundry sand is called “greensand”, because of the slight moisture content.
A combination of sand, clay and water.
Category: Basic Skills
Molding
Greensand molds with gating system.
Gating iron (Latin: ferrous) is different than gating aluminum or bronze (non-ferrous). Dross is produced with non-ferrous alloys , but NOT with iron. Dross is similar to the foam on top of beer.
When gating non-ferrous castings, dross is carried beyond the gate by the deep runner, clean metal enters the casting.
When gating iron, the metal is so heavy, 2 large openings (sprue/riser) are used to equalize the pressure.
Parameters of Gating
Alum castings 3lbs. or less- Bronze castings 9lbs or less
1/2″ sprue, 1″x 1″ runner up to 10″ long.
Alum castings 3-8 lbs.- Bronze 9-24 lbs.
3/4″ sprue, 1.5″x 1.5″ runner up to 14″ long.
Alum castings over 8 lbs. Bronze over 24 lbs.
1″ sprue, 2″x 2″ runner up to 18″ long.
Gallery
Recyclers call it “red-brass”(bronze) or “yellow-brass”(brass).
Patterns
A casting is a copy of your “pattern”. Sand is packed around the pattern and carefully removed. A slight draft is necessary on vertical surfaces (sides), like the way “stacking cups” work. Patterns can be made of wood, plastic or metal. Wood patterns should be sealed to prevent moisture being robbed from the sand. Shellac or paint work well.
When making a pattern, increase size 2% for shrink and a % for machining, depending on finish.
Apprentice Test
This casting is a symbol of achievement and excellence in the foundry industry. This test of molding skill originated many years ago in the British Isles. Foundrymen there considered molding an art. An apprentice had to spend many years learning and practicing the trade before becoming a Journeyman.
Continue reading “Apprentice Test”Flasks
Many projects require a special size of flask, making them yourself is a necessity.
Continue reading “Flasks”