1.1   This British Standard provides data for the estimation of the equivalent diameters of pieces of steel of relatively simple shape (hereafter referred to as 'objects').

The information is not confined to one type of product, e.g. forgings as distinct from castings or rolled plate, but refers to all objects undergoing a cooling process from an elevated temperature down to ambient temperature by being allowed to stand in still air or by immersion in oil or water.