A clean-looking whetstone and a corrected sharpening surface are not the same check. Shapton’s FAQ recommends correcting the surface before sharpening and gives a pencil-grid method as one indication of where the correction tool has made contact. It also distinguishes the construction of its correction tools.
Technique and structure
Shapton describes 空母 as a cast-bronze correction surface with electrodeposited diamond, while なおる uses a ductile-cast-iron surface with separately applied correction powder. The abrasive is therefore supplied in different ways, even though both tools serve surface correction. The FAQ’s pencil-grid method marks the stone before correction: a disappearing line indicates a place where the tool has contacted it. That is a contact indication, not a universal guarantee of the finished surface’s condition or compatibility with any abrasive tool.
Check the finishing surface too
For KUROMAKU finishing stones, the maker warns that a roughly corrected surface can prevent good sharpening and specifies a finely finished surface. It says it has not verified correction with other manufacturers’ diamond stones; their grit and surface condition can affect the result. Its own correction tools are not recommended for correcting diamond stones because their correction surfaces may be damaged.
For international readers
Choose the correction method for the actual stone and follow the maker’s tool-and-powder guidance. This complements our earlier [grit, water and storage guide](/posts/shapton-whetstone-water-grit-and-storage-guide/); it does not assign another brand’s grit equivalence or turn every diamond abrasive into an interchangeable flattening tool.
Global shipping and buying
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日本語
砥石の面直し：鉛筆の格子と修正器の構造
シャプトンのFAQは、刃物を研ぐ前の砥面修正を勧め、鉛筆で引いた格子が消えた場所を修正器が当たった目安と説明しています。「空母」は青銅鋳物へのダイヤモンド電着、「なおる」はダクタイル鋳鉄に修正用パウダーを振りかける構造と区別します。仕上砥の粗い修正面や他社ダイヤモンド砥石の未検証条件もあり、面の汚れを落とすことと、平面や仕上がりを整えることを分けて確認します。