Hardness change

There was a knife that had to be returned because Aike occurred during the rough sharpening process with Mr. Doi’s knife. Normally, Mr. Doi casually tosses such knives into a drum can designated for disposal at his workshop. However, I had received one for practicing engraving, so I decided to try my hand at it.

To make the most of a single knife, I practiced engraving using the entire flat section! I engraved the name into the soft iron part from the blade edge to the tip. The key to successful engraving is not doing ◎◎ (^^) *◎◎ is a secret.

Setting that aside… using a tool called Tagane, I engraved the name. The dull sound of knocking! Since I was engraving on the soft iron part, the lower hardness produced a lower sound (perhaps influenced by the width of the blade? Similar to the principles of a xylophone?). As I progressed towards the blade edge, the sound changed. It went from a knocking sound to a crisp, high-pitched one. I initially thought it was due to the narrowing width, but then I noticed that the Tagane was having trouble biting into the surface… It was more like slipping! This phenomenon is often observed with hard knives (like Honyaki).

This is purely speculative, but as Mr. Doi mentioned before, the hardness may differ between the blade edge and the tip. It’s not about the initial hardening but likely related to the tempering process. While physically tempering the knife, such as in a quasi-heat storage environment, creates a knife with resilience, it results in uniform hardness from the blade edge to the tip…

For knives like Deba, where you strike with the blade edge and do the cutting with the tip, this difference can affect ease of use. The art of manual tempering, achievable only through the craftsman’s intuition, brings about this sophisticated transformation! As a sharpener, it means adapting to the changes in hardness, but from a knife perspective, it turns into a high-quality tool.

There’s something unseen, whether it’s physical or scientific, in the world of Sakai knives. Oh, the engraving part? What happened to that? Show it to you?? Please forgive me, I’m still in the learning process(lol).

hibishugyo　

• 2007-11-29