Although this hard metal cutting tool developed in Germany is strong against compression stress, it is known in the die level that it will be broken when stretching stress is generated, and a Japanese sword is structured to generate pronounced stretching stress, which makes some people doubt the credibility of this experiment.
しかし、このドイツで開発された超硬合金製の刃物は圧縮応力には強いものの、引張り応力が発生すると破損することが金型では知られており日本刀は顕著な引張り応力が発生する構造なのでこの実験の信憑性を疑うものもいる。