I believe that much of the problem w/ using a hatchet as a hammer depends on what you are hitting. It has nothing to do w/ the hardness of what you are hitting, but it's mass. A person could drive nails into a stump for years straight and never hurt a thing. If you attempted to drive a hardwood wedge into a knotted log, the face of the hatchet will stop, and the edge will want to keep going. That is where the deformation of the poll comes from. I have seen pictures of this, but it was in larger tools. I think that the less moveable the target, the more of a risk you are taking.
Edited to add: I just went and looked at my old Craftsman hatchet, which I had been using as a field expedient hammer on some hot steel and a 100 lb anvil. The poll is fine after maybe 80 or so heavy hits. Not neccesarily the same as wetterlings/gransfors.
Edited to add: I just went and looked at my old Craftsman hatchet, which I had been using as a field expedient hammer on some hot steel and a 100 lb anvil. The poll is fine after maybe 80 or so heavy hits. Not neccesarily the same as wetterlings/gransfors.