Ore (soft iron) is added to the metal of the blade (steel) as part of the process to produce the shape of the knife.  In the "welding" process, borax and an iron oxide are used as binders. The ore is heated to approximately 900 degrees in a furnace; and then formed into shape by beating with a belt hammer.

During forging, defects and kinks are pounded out, excess material is removed, and rough sharpening is done as part of the process to arrange the shape. Carved seals of various types of metal are hammered into the blade.

A coating of clay mud is applied.  After drying, the blade is fired in a furnace at about 800 degrees and then rapidly cooled.  With tempering, the steel hardens. The blade is then heated until it is viscous at a temperature of about 150-200 degrees and then slowly cooled. This is called the re-firing process. The determining factor of a quality knife is the balance between hardness and viscosity.  This is an extremely difficult process, one which determines the feel of the blade.  Afterwards, any distortions resulting from firing is pounded and eliminated with a hammer (balancing).

Polishing involves the meticulous and arduous process of using a succession of rough whetstones gradually ending with finer whetstones. The temperature increases in polishing of the blade prevents distortion and strength degradation in  the blade.

The core of the blade is driven into a wooden haft completing the finished product after final adjustment.  Japanese knives have the advantage of fitting a new haft should the old wooden haft decays.