rough grindstone; coarse whetstone
A sharpening stone with a coarse grit, used for initial shaping or repairing blades.
For a chipped kitchen knife, first sharpen it with a coarse whetstone.
Standard kanji spelling for a coarse whetstone.
Alternate kanji spelling; 荒 also conveys roughness.
Compound of 粗 (ara, 'rough, coarse') + 砥 (to, 'whetstone, grindstone').