A good Japanese style forging hammer is not something most smiths can simply pick up at the local supplier, so making one yourself is the practical route. That is the problem this build takes on, and Daniel Lea handles it by forging the whole tool from scratch, beginning with a plain billet of C45, also known as 1045, steel.
The starting stock measures 150mm, or 6 inches long and 1 3/4 inches across. It is heated in a coal forge, set on the anvil and held with heavy tongs while a punch is positioned to form the eye hole and struck with a sledgehammer. An eye drift then goes into the opening and is driven through to widen and shape the socket, and the eye lands 2 inches from the rear of the head.
The details that stand out to me are the faceted, octagonal bevels on the head and the textured surface around the eye, plus the dark-stained or charred wood handle, which suits that faceted geometry nicely in my view. Top fullering and flattening tools profile the cheeks, and the piece is reheated over and over and brushed free of forge scale between rounds.
The finished hammer comes out at 6 inches long and 1 3/4 inches in diameter, ready for metalworking and forging work. Coordinating the placement and force of every strike is the part of this I find most admirable. Two questions stay open for me: whether the longer length or the cylindrical shape does more for vertical force transfer, and whether the head was tempered after one face was hardened.
Project by Daniel Lea. Watch it on their YouTube channel: