Process of Forging & Shaping a Tanto Blade

A charcoal fire is used to heat the steel for shaping with hand hammers. I often use a heavy hammer for rough shaping and a lighter one for the finishing work. The shaping of a blade is divided into a hot and a cold stage, and each stage further divided into two steps. First a specific type of blank (sunobe) is forged, the shape of which will determine the finished dimensions of the blade. Then the blank is forged into the shape of the blade and allowed to cool slowly. The cold shaping begins with the profile and then moves to the bevels. Once these are finished, the blade is ready for Yaki-ire, clay tempering.


Forging the Blank (Sunobe)

In this stage, the volume of steel is allocated to each area of the blade and tang. This distribution will largely determine things like distal taper, proportions, and style of the blade, though the sunobe looks very little like its final shape at the end of this step. In traditional swordsmithing, a practiced eye can determine the outcome of a student’s test at the sunobe stage, without even waiting for the forging of the final shape.

Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
The blade in the foreground is the raw material, a 24″ mill saw blade made of lovely steel that I have used for several projects.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
The hammer that I use for most of the shaping work, made from a piece of axle (You Need A Japanese Swordsmith’s Hammer).
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
The tip begins as a reversed 45 degree angle, the longer side will become the cutting edge and tip.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
The completed sunobe, the straight side will become the cutting edge once the bevels are forged in.

Forging to Shape (Hizukuri)

Forging a sunobe into the shape of a blade is a process of working up and down the steel a section at a time, forming the bevels and establishing the geometry of the knife. As the bevels are narrowed, the outward moving steel tends to curve the blade away from the edge, this must be anticipated and compensated for throughout the process. If it is not addressed early on, there will be no way to correct it later. Keeping the temperature as low as possible and forging almost into the black range each heat is one way to help refine the grain structure of the steel. Enough edge material must be left to have a 2mm thick edge after filing and before yaki-ire.

Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
Back into the fire.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
A spine view showing how the blade tapers away from the mune machi in both directions.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
The tang is forged very close to its final shape, but the notches for the mune machi and ha machi will be filed rather than forged in on this very small blade.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
Forging with water on the anvil creates steam explosions which blow off the fire scale, keeping the steel clean and free of impurities.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
After forging, the blade is cooled slowly in charcoal ashes to make it as soft as possible for the cold shaping and filing stages.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
The completed forged blade, the notches for the machi have been marked with a file. The clean, smooth steel is a result of the water forging and carefully placed hammer blows.

Rough Shaping (Ara-Shiage)

This stage of cold shaping has two distinct steps, the first to outline the profile, and the second to establish the bevels and sides of the tang. Files are used to profile the blade in a blacksmithing leg vise, adjusting and refining each line slowly, removing to check the overall silhouette often. A sen dai (staple vise) and a sen scraper are used for the rough work on the bevels, filing and drawfiling for the final work. The edge should still be 2mm thick after all of the rough shaping is finished in order to reduce the risk of warping or cracking during yaki-ire.

Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
The mune has been cleaned and straightened in the foreground, the notch for the mune machi is beginning to take shape.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
The completed profile clearly shows the tang and the blade outlines now.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
At this stage, nothing has been done to the bevels yet, this is still the water forged steel skin.

Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
The sen scraper is used remove the tough fire scale and to take down the excess material on the tang.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
One edge is established, then the other, and finally the material in between is removed.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
Drawfiling removes the marks of the sen and levels the surface out.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
The tang is rough finished, the blade is next.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
A view of the sen dai, showing how a series of wedges and blocks can quickly create a custom hold for any blade geometry.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
A clear example of the technique of setting the finished height of each edge on an angle before removing the centre material.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
Finished by drawfiling.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
Compound angles and a non-marring grip created by multiple angled wedges in the sen dai.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
Grinding with a slab of local sandstone to check the surfaces and get the feel of the geometry on a stone.

The next process is Yaki-Ire, clay tempering.