The time comes when even the best blacksmith will come upon an item that he can do nothing with, or may find he badly needs a certain material in order to finish a vital repair. In times like this, he can take almost any armour and melt it down, or form it into a reworkable mass. This way he may not have to go find raw material himself, he can just get by with what he has on hand. If you want to make sure you don't cannibalize wrong item, place the item in keep.