Cast and forged parts such as crankshafts and cams have a different appearance, one that an experienced machinist can recognize by look and feel. Cast items will have a thin, straight parting line where the molds met, while a forged part will have a wider, ground flat area where the excess material was cleaned up after the forging process was roughed out. Steel and cast iron also produce a different shape and color of sparks when touched to a grinding wheel.
Jerry
