砥石の番手
The grit number on a Japanese whetstone is not a measurement you can compare across makers. There is no dominant standard behind it.
Wikipedia’s article on sharpening stones states the problem plainly: there is no dominant standard for the relationship between grit size and particle diameter. Part of the reason is that “grit size” is used to describe the smoothness of the finish a stone produces, not only how large its particles are. The finish also depends on the shape of the abrasive particles, how much of each is exposed by the binder, whether they fracture into smaller ones under pressure, their hardness, and what they are made of.
So two stones stamped with the same number can cut differently, and a number from one maker does not transfer to another. What does transfer is the rough progression: around 200 for reshaping a damaged edge, around 500 for producing a sharp one, 1000–2000 for an edge finer than most factory edges, and 4000 and up for polishing. Those are the figures the same article gives, and they are the level of precision the number can actually support.
Natural Japanese stones are a separate case again: they are classed as ara-to (rough), naka-to (medium) and shiage-to (finishing), and converting those classes to a grit number is difficult because the classes are broad and a natural stone has no inherent grit number at all. A natural stone sold with a number attached has been assigned one by somebody.
For a single-bevel Japanese knife the usual starting pair is a 1000-grit stone to sharpen and a 3000-grit to polish; Japanese Knife Lab recommends exactly that pair from the start for yanagiba, with 6000 and above as an optional mirror finish. Buy the pair rather than one stone: a fine stone alone cannot restore an edge, and a coarse stone alone leaves it rough.
Read the number as a band rather than a figure, and compare stones within one maker rather than across makers. If a listing gives a grit number and nothing else — no maker, no indication of whether the stone is synthetic or natural, no statement of what it is for — it has told you less than it appears to. The pairing matters more than the precision: a stone to sharpen and a stone to finish.
There is no shop link on this page. The honest version of the advice above is “buy a 1000 and a 3000 from the same maker”, and which maker is exactly the judgement this site cannot make without owning and using the stones. The knife guide it follows from is linked below.
Sources The other guides鉄瓶と鉄急須
One boils water and gives you iron. Putting the other on heat cracks its lining for good.
土鍋の目止め
Unglazed clay is porous until rice starch seals it — one simmer, once.
漆器の手入れ
Dishwasher, microwave, sunlight. All normal, all irreversible on urushi.
片刃と利き手
Ground on one side only. The wrong side does not cut badly — it does not work.
土鍋とIH
Induction heats metal, not clay. Most donabe never get warm — and cannot be converted.
熊野筆の毛
Not a quality ladder. Natural hair holds powder; synthetic is built for cream and liquid.
茶筅の穂数
Carved from a single piece, so a snapped tine is not a repair. The tine count is a spec, not a score.
錆と経年変化
One protects the blade, the other eats it. Scrubbing the wrong one leaves the knife worse off.
三徳・牛刀・菜切
Two of these are the same knife. And a nakiri suits either hand; the usuba it resembles does not.