Japanese
樋
Definition
Hi is a groove engraved along the blade on the shinogi-ji or hira-ji area. Originally the main purpose of these grooves was to reduce the blade's weight and improve its cutting ability. Later grooves served as a decoration or even as a way to conceal flaws.
Grooves are classified according to shape and location with terms describing the top of the groove ending with -hi (樋, usually pronounced as -bi when preceded by other characters) or -tome (止め) for features at the bottom of the groove (known as tome).
Hi
- bo-bi: A continuous straight groove of notable width, known as katana-bi on tantō. With soe-bi, a secondary narrow groove follows the inner straight length of the main one. With tsure-bi, the secondary is similar but continues beyond the straight length.
- kage-bi: A small groove beside a regular groove of a blade. Yamanaka mentions that this was an old term for soe-bi.
- futasuji-bi: Two parallel grooves.
- shobu-bi: A groove shaped like the leaf of an iris plant.
- naginata-bi: A miniature bo-bi whose top is oriented opposite from the blade's, and usually accompanied by a soe-bi. Seen primarily on naginatas.
- kuichigai-bi: Two thin grooves that run the top half of the blade; the bottom half is denoted by the outer groove stopping halfway while the inner one expands to fill the width.
- koshi-bi: A short rounded-top groove found near the bottom of a blade, near to the tang.
Tome
- kaki-toshi: The groove runs all the way down to the end of the tang.
- kaki-nagashi: The groove tapers to a pointed end halfway down the tang.
- kaku-dome: The groove stops as a square end within 3 cm of the tang's upper end.
- maru-dome: Similar to the kaku, except with a rounded-end.
