There exists some mispresentation of the Japanese tanto among knife industry marketing. Typically the sales pitch one might encounter might describe the tanto as a "reinforced armor-piercing chisel point". Or words such as "a broken sword meant an unbreakable knife."

As you can see from the above illustration, the historical common tanto was of a hira-zukuri style which bears little resemblance to the Americanized tanto. The closest would be the shinogi-zukuri (middle illustration). Though hard to see, the blade has a very subtle curve and the lines follow a proper width taper. Further, the tip is not triangular as in the Americanized Tanto but rather follows the arc of a larger circle.

Observe the Americanized Tanto closer. This is based on the design of a production knife manufacturer. Notice how the back and the ridge line (shinogi) are parallel but the edge profile is providing the curve? This is aesthetically imbalanced. Further, the yokote vertical line marking the beignning of the tip is at an odd angle. Finally, the tip is triangular. In properly made tanto, the blade naturally curves from traditional clay-application and heat treatment. However, in the case of factory-ground blades where a differential heat treatment is not achieved (dual hardnesses in edge and body) but rather the blades are through-hardened (singular hardness throughout) if a curve is to be ground into the steel, the back and ridge lines should not be parallel but follow the curve of the edge. In short, this blade design is inelegant and the tanto could benefit from its historical counterpart.

One question of interest is this: would the Japanese recycle broken blades into shorter knives? Consider for a moment that assuming indentical blade widths and thicknesses, a blade of shorter length would be less prone to breakage than a blade of longer length. Knives are not swords and the structure of both knife and sword blades withstand shock and lateral stresses differently.

It is not impossible for a tanto to be a reground broken katana tip. However, there are very few tanto made in the common/standard shinogi-zukuri style to begin with, howbeit tanto that are verified as recycled from broken katana tips that survive today. Typically the Japanese tried to make swords that would not break. The edges were harder and the bodies softer (softer meant tougher and more able to withstand shock) and such a structure would mean that the sword would resist bending but would still bend if subjected to enough lateral torque; the sword would bend before it would break. If the hardened edge cracked there was still possiblility of restoration by grinding the edge back behind the crack and starting the edge from there, so long as there was still enough yakiire (hardened edge) to make the sword useable.

If the chip or crack in the yakiire entered so far back that it structurally compromises the safety of the weapon, the sword would typically be completely reforged, as steel was precious, thus it was less likely for it to be reshaped into a tanto and the latter half discarded. However if the blade had significant family value (e.g. generational heirloom) then it might be left alone and a new sword altogether would be forged.

ILLUSTRATION BY ADRIAN KO