Every line in the dataset, and how firm the ground is
335 entries across 56 lines. 111 standard-defined, 137 maker-published, 84 estimated. Only 133 carry a published distribution; the other 202 are single points, the spread unknown. The bar on each line shows that mix, firm ink to faded.
Our one design choice
A common scale to read every grit number against
A grit number is not a measurement. P400 sandpaper, a #400 waterstone, and a 400-mesh diamond plate are three different sizes, and even two #1000 waterstones from different makers rarely agree. No single standard covers all of them, so to read one product against another the table needs one shared yardstick, and we had to choose it.
We use JIS R6001, the Japanese microgrit standard. It spans the widest range sharpening actually uses (#240 to #8000), defines each grade by a measured distribution rather than a single number, and its numbers are the ones most waterstones already reach for. We fit a smooth curve through its grades so any number maps to a micron, and extend past its ends by continuing the standard's own trend, marked uncertain because no standard defines those grades. It is not a new standard and does not replace JIS or ISO. It is a reading aid: one place to ask where a grit number actually lands. Every product page shows that equivalent.