Forging Steps of a Katana
In an age of mass production, the katana that the Hanwei Forge offers are
still hand made by skilled craftsmen. While the power hammer has replaced
some of the back-breaking labor, these katana are made using a process very
similar to the one used centuries ago.
The first step is creating a billet of super high-carbon steel. The
blade is formed using a hot forging process. The steel is heated and repeatedly
hammered into shape. The forging process aligns the crystalline structure
of the steel to create a stronger blade. It provides an even dispersion of
carbon throughout the steel providing a uniform strength throughout the finished
The forging process leaves a heavy oxide coating called scale. The
scale is removed and the blade is shaped roughly to the needed dimensions.
The steel was allowed to cool slowly at the end of the rough forging stage, so
it is still in the annealed (soft) state. The blade is still straight at
this point and will not take on a curve until quenched.
A special clay is applied by hand to the blade. The clay is thin on the edge
and thicker on the rest of the sword. The thinner the layer of clay, the
quicker the steel underneath will cool during quenching. This will create
a hard edge that will keep sharp and a softer spine that will keep the sword
from breaking. A pattern created in the clay coating will created the
distinctive hamon (temper line) in the finished blade.
The quenching step is the most critical part of the operation. The blade,
with its clay covering, is heated and then quenched in a water bath. The
critical temperature of the steel is determined by the color it glows.
After reaching the proper temperature, the sword is then quenching in water.
The shape and continuity of the hamon (temper line), the sori (blade curvature),
and blade straightness are all determined by the care and skill exercised in
The last adjustment to shape of the sword are made at this stage. The
final curve (sori) may be adjusted to set the point of balance and point of
percussion. The heavy oxide scale is removed and the blade is rough
polishing to finalize the size the dimensions. The habaki (blade collar) is then
custom made to fit each sword.
The last step is finish polishing. This process define ridgelines and
other surfaces. The surfaces of the blade must be carefully polishing to
preserve the crisp lines of the blade. This step must also bring out the
beauty of the hamon (temper line).