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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.

Rough Forging

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 blade.

Rough Shaping

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.

Clay Covering

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.

Quenching

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 quenching.

Sizing

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.

Finishing

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).