Ahab decides that he wants to ask the blacksmith to forge him a new harpoon, for use in catching the white whale, whom Ahab now calls ‘the white fiend.’ Ahab throws down before the blacksmith a set of old tacks used in the hoofs of “racing horses,” saying that there is no stronger metal to be used in the making of the harpoon.
Ahab now sees Moby Dick as a kind of devil, an interesting fact because other characters have seen both Ahab and Fedallah, whom Ahab has brought expressly to kill Moby Dick, as being devilish too.
The blacksmith begins the work on the implement, but Ahab interrupts him, saying the harpoon is not perfectly smooth, and asking to do the smoothing himself. Ahab also notes that Perth can smooth out any flaw but one—the “flaw or wrinkle” in Ahab’s own brow and mind, caused by his hunt for the White Whale. Once the harpoon has been completed, Ahab asks the three harpooners if they will be pricked by its barbs to “baptize” it, and they agree. Ahab takes away his new steel weapon, ready to use it in the hunt for Moby Dick.
Ahab's comment about the un-smoothable "flaw" in his mind indicates his awareness of the wrongness of his monomania, and to some degree suggests that Ahab is as much in thrall to that monomania as are all the members of his crew. The baptism of the harpoon in the blood of the harpooners is a perversion of the Christian rite of baptism—rather than a baptism in water celebrating life and rebirth through Christ, the harpoon is baptized in blood to consecrate it as a tool of death. The strange forging and baptism of the harpoon only heightens the tension toward the conflict between Ahab and Moby Dick. But Ishmael continues “putting off” this confrontation, by still inserting other “fugue” chapters, and descriptions of further preparations aboard the ship, as it approaches the seas off Japan.