Bob Hackett
I would say that a hammer is a tool used to strike (or drive) something else. Blacksmiths top tools are in the realm of tools that are struck by hammers so they really aren`t hammers themselves. They are more like cold chisels or stamps with hammer like handles.
Those double clawed "hammers" (the ones will claws only and no striking face) have more in common with nail,pinch or wrecking bars than they do with functional hammers. Granted the cheek could be used to drive a nail but then you`d scar up the cheek of the "hammer" and the wood as well when you finally drove the nail flush.