| Watts Shop Performance |
| Manufacturing Methods |
| Parts May be cast, forged or machined from a solid billet. Cast parts are made by pouring molten material into a mold, letting it cool, then pulling it out and machining it. Cheap and easy, the resulting nonuniform grain structure limits strength. By contrast, a forged part is molded into shape using costly giant machines, refining the existing grain structure. A variation on forging is powdered metal technology, a quasi forging process where metal powder is poured into a mold and heated (like casting), then hot struck into final shape (like forging). The end result is stronger than a casting and more uniform with less weight variation than a traditional forging. Many late model stock steel rods use powdered metal technology with good results. With big, complex parts like a crank, forging's full theoretical benefits may not be realized because economics dictate compromising the design to accommodate multiple parts from the same tooling. Even though it does interrupt the grain flow, today the trend is to machine high end cranks out of premium billet material; but forging is still preferred for smaller, less complex structures like connecting rods. |