Combinations of operations covered by different sub-classes are dealt with in Fulltext... Hierarchy... Expanded...B23P. Combinations of operations covered by any particular sub-class with operations covered by other classes, e.g. with operations involving removal of material, are also dealt with in Fulltext... Hierarchy... Expanded...B23P, except that if the operations covered by the other classes are subsidiary to the operations properly covered in a single sub-class of Fulltext... Hierarchy... Expanded...B21 the combination is classified in that sub-class.
Processes of a kind covered by this class but applied to non-metallic materials may be classified here if they are applicable to metal and cannot be classified fully in one other class.