AFS grain fineness number

Evaluation unit established by the American Foundry Society for grain size rates for molding and coresand materials.

The relevance of the grain fineness number can be ascribed to the fact that this values is proportional with the number of grains per unit of weight and with the specific surface area of the sand. For approximate calculation of the AFS grain fineness number, the value of the theoretic specific surface area is multiplied by the factor 0.57. For more details, please refer to the VDG bulletin P 34.