Japanese Whetstones: Grit Chart, Brands and How to Use Them

A Japanese whetstone (砥石) — by definition a sharpening stone, called toishi in Japanese — is a flat bench stone you sharpen a knife on with water. This guide covers what the grit numbers on Japanese water stones actually mean (with a grit chart in microns), which grit to use for Japanese knives, the main brands — King, Shapton, Naniwa, Suehiro and others — how long to soak each one, how to use and flatten a whetstone, natural stones, and how to buy them from Japan. Prices are tax-in yen from Japanese shop pages on October 31, 2026.

Japanese Whetstone Grit Chart: Grit Levels in Microns

Japanese whetstone grits use the “#” scale of JIS R 6001-2, the Japanese standard for bonded abrasives (stones and wheels). It has 18 “#” steps from #240 to #8000, read as “ban” — #1000 is senban. The number stands for the median size of the abrasive grain: the higher the number, the finer the grain.^[38][39] JIS gives two micron values per grit because the grain can be measured two ways, so a #1000 stone works with grains of about 11.5 µm or 15.5 µm depending on the test method.^[38]

Use it as a grit comparison chart for Japanese stones. Source: JIS R 6001-2:2017, tables 4 and 5.^[38][39] The “typical job” column follows the grit bands makers publish (see below).

Understanding whetstone grit: what the numbers mean and which grit first

A lower grit number means a coarser stone that removes metal fast; a higher number means a finer stone that polishes. Go from lower grit to higher grit: coarse, then medium, then finishing stones are normally used in that order.^[40] The highest grits sold by the makers here are Suehiro’s Gokumyo #20000 and Shapton’s #30000.^[41][25] For razor edges and straight razors, the classic answer is a hard finishing stone (awase-do), which Kotobank describes as the finishing stone for razors; Tojiro reserves #8000+ for super-finishing.^[42][1] Whetstone grit colors are maker-specific: Shapton color-codes Kuromaku by grit, and King’s #1000 is brown and its #6000 pale yellow.^[25][7]

Japanese grit vs US and European grit (ANSI / FEPA)

The same number does not mean the same size in every system. A Japanese whetstone shop gives JIS #1000 as about 14–16 µm, FEPA P1000 as about 18–20 µm and ANSI 600 as about 16–23 µm.^[43] Coated-abrasive charts put P1000 at 18.3 µm and P2000 at 10.3 µm, close to CAMI (ANSI) 500–600 and 1000–1200 respectively.^[44][45] Treat cross-system “equivalents” as rough: FEPA P and CAMI grades are for sandpaper, while JIS R 6001 covers stones and excludes sandpaper.^[38][44]

Shapton’s grit-to-micron scale

Shapton is the one maker in this guide that prints a micron “class” (median grain size) for each grit on its Glass Stone and RockStar lines.^[13][46]

Each maker grades on its own scale, so a #1000 from one brand can feel different from another’s — a Japanese whetstone shop notes that the grit number is an average and that the feel also depends on hardness.^[43]

What Grit Whetstone for Japanese Knives?

Makers sort stones into three bands — coarse (ara-to), medium (naka-to) and finishing (shiage-to) — but draw the lines in different places:^[40]

• Is a 1000 grit whetstone enough? For routine sharpening at home, yes, by most makers’ advice. King Toishi tells beginners to start with a King Deluxe #1000, which “restores enough sharpness” for routine maintenance; Tojiro says a first stone can be just a #1000 medium; and Kai says #800–#1000 is enough for everyday sharpening.^[21][47][2]
• Coarse 220–400 grit: only for chips or reshaping. King suggests a #300 for chips.^[21][1]
• Finishing 3000, 5000, 6000 and 8000 grit: for a sharper, more polished edge after the #1000. King points to #6000; Shapton recommends Orange #1000 + Wine #5000 for household knives (and Blue #1500 if you buy one stone); Tojiro reserves #8000+ for sashimi knives.^[21][14][1]
• Grit progression (a grit recommendation by step): Suisin suggests roughly doubling the grit at each step, such as #400 → #1000 → #3000.^[4]
• Stainless kitchen knives: Suehiro says a #500–#1500 is “fine to stop here”, and a finishing stone is generally not needed; hand-forged knives get #600–#1500, then #3000+ for a light finish.^[3]

A combination (combo) stone gives you two grits in one block, one on each of its two sides.^[2] On the King KW-65, the brown #1000 side is for when the knife has gone dull and the pale-yellow #6000 side is for finishing: start on the brown side, finish on the yellow.^[7][6]

Japanese Whetstone Brands

King (King Toishi)

King stones are made by King Toishi in Tokoname, Aichi, founded in 1940 as a synthetic-stone maker; King Deluxe was developed in 1958 and went into mass production after the Oso factory opened in 1965. The company uses a clay (vitrified) bond for medium stones, a resin bond for finishing stones and a cement bond for coarse stones. King-series stones are sold through Matsunaga Toishi, an Osaka trading company founded in 1948.^[20][21] King Toishi says a stone lasts “several years or more” in normal home use, and its 10Good line teaches a 20° knife angle with a dot-grid guide on the stone.^[21][48]

The KDS is the same #1000/#6000 pairing on a base (207 × 66 × 36 mm); the G-1 #8000 comes with a nagura stone for truing the surface.^[6][11]

Shapton

Shapton makes its stones in Mashiko, Tochigi.^[25] Its three main lines:

• Kuromaku (刃の黒幕, “Kuromaku” on the English site): 15 mm solid stones, 210 × 70 × 15 mm, about 500 g, with a case that doubles as a stand — Shapton calls it the world’s first whetstone color-coded by grit.^[25][13]
• Glass Stone: a 5 mm stone layer on 5 mm tempered glass, 210 × 70 × 10 mm and about 360 g, in grits up to #30000.^[13][25]
• RockStar: solid 210 × 70 × 10 mm stones, about 370 g, #320–#16000.^[46]

Source: Shapton.^[25] Ueda Kanamono listed Kuromaku #120–#320 at ¥3,125, Orange #1000 at ¥3,208, Green #2000 at ¥3,726, Wine #5000 at ¥4,840 and Melon #8000 at ¥6,186 on October 31, 2026.^[26] Shapton stones sharpen everything except ceramic and cemented-carbide blades.^[13] Accessories include the Glass Stone Holder 50200, the Field Holder 50300 (which doubles as a case) and 3-stone sets such as 50308 (#500 / #2000 / #8000 with holder); the Diamond Glass Lapping Plate is part no. 50100.^[25]

Naniwa

Naniwa Abrasive was founded in Osaka on October 10, 1941 by Torao Sadakane and incorporated in 1952; it makes stones at factories in Shiga and Vietnam and moved its head office to Chuo-ku, Osaka in September 2025.^[27][28] For the EU, US, Canada and Australia it sells export lines: Naniwa Pro (Chosera / Chocera Pro, formerly Professional Stone, 210 × 70 × 20 mm, in #400, #600, #800, #1000, #2000, #3000, #5000 and #10000; and Diamond Pro), Naniwa Advance (formerly Super Stone, 20 mm and 10 mm, #220–#12000), Naniwa Standard (formerly Traditional) and Naniwa Basic combination stones (#220/#1000 and #1000/#3000, 185 × 65 × 30 mm).^[29] Naniwa says its Japan-market models are made for use in Japan, that it does not sell or ship them abroad, and that returns or exchanges can’t go through overseas retailers — so US buyers are better served by the export lines from a US dealer. For Naniwa Advance vs Chosera: Advance is the former Super Stone for professional and semi-professional users, Chosera Pro the professional line. Naniwa also sells a stone holder (A-902) and a Sink Bridge (IZ-1121) for sinks 290–550 mm deep.^[29]

Suehiro

Suehiro, in Niigata City, has made Suehiro-brand synthetic stones since 1967 and does its own mixing, pressing, firing and finishing; it states that up to medium grit, synthetic stones beat natural ones on quality.^[30][16] CERAX is its standard line: the CERAX 1010 (#1000, about 205 × 73 × 29 mm, about 1,000 g) lists at ¥3,600 before tax and sold for ¥3,960–¥6,567 on Rakuten on October 31, 2026.^[49][31] The NEW CERAX CR-1000-B (#1000, about 950 g) comes with a case that works as a water tray and holder; RIKA 5000 is a #5000 finishing stone with a nagura stone; DEBADO (LD-21 #180, LD-101 #1000, LD-601 #4000), Gokumyo (up to #20000 — the “20k” GMN200, ¥30,000 before tax), Kouseki and Dual Stone are non-absorbent, splash-and-go stones. For a large (XL-size) stone, the CERAX 3030 measures 225 × 90 × 60 mm.^{[50][51][16][52][41][53]}

Other Japanese stones: Sigma Power, Atoma, Arashiyama, Morihei, Kitayama

• Sigma Power (Tokyo, founded 1956 as a whetstone shop) makes the Select II ceramic line, #240–#13000; a Rakuten retailer says to let every grit absorb plenty of water before use. Sigma’s own shop says it cancels orders placed through overseas forwarding services, so use a marketplace listing instead.^[32][18][54]
• Atoma diamond plates are made by Tsuboman in Kure, Hiroshima (a file maker since 1867, diamond tools since 1981) in #140, #400, #600 and #1200; the stone-flattening Atoma comes with a handle, and Tsuboman positions it for hard stones.^[34][55][36]
• Arashiyama stones are sold by Imanishi Seito in Kyoto; the Arashiyama #1000 medium stone was ¥3,520 at Toishiya.^[56][57]
• Morihei (Asakusabashi, Tokyo, founded 1933) sells the 火 (Hi) series; a retailer lists the Hi #1000 at ¥7,480.^[58][59]
• Kitayama #8000 is an Otani Toishi stone (resin bond, with a wooden base and nagura), ¥4,880 at Toishiya Ao.^[60]

Whetstone Material: What Japanese Sharpening Stones Are Made Of

Synthetic stones are made of an abrasive held by a bond. The abrasives are silicon carbide (C/GC, the abrasive once sold as Carborundum, used in coarse stones), fused alumina (WA, aluminum oxide, the all-rounder) and diamond; the bonds are vitrified (fired clay), resinoid (resin) and magnesia. Artificial (synthetic) stones give consistent grit; natural stones are quarried rock — sandstone for coarse stones and fine siliceous slate for finishing stones.^[61][40][62] That is the main difference between sharpening stones of the same grit: the bond affects how fast the stone wears, how much water it needs and how it feels.^[61][63]

Oil or water on a Japanese whetstone?

A Japanese waterstone (water stone) is used with water. Shapton says oil can be used, but once a stone has had oil it must stay an oil-only stone; Kuromaku can also be used as an oil stone, and Suehiro’s Dual Stone works with water or oil.^[13][25][16]

Soak or Splash and Go? How Long to Soak a Whetstone

Not every Japanese water stone should be soaked. Follow the maker’s rule for your stone:

As a rule of thumb, Kai says to soak a synthetic stone until the bubbles stop (it gives 10–20 minutes), and Tojiro about 5 minutes; Sakai Ichimonji says clay-bonded (vitrified) stones need soaking but resin- and magnesia-bonded stones should not be soaked, and you can tell them apart because vitrified stones bubble a lot.^[19][64][63] Don’t leave Shapton stones in water for more than 30 minutes, and don’t use hot water.^[14]

How to Use a Japanese Whetstone: Step-by-Step Instructions and Technique

1. Set up. Soak if your stone needs it, set it on a holder or a wet cloth at about navel height, and keep the surface wet — a dry surface heats the edge and clogs the stone.^[19][65]
2. Find the angle. For a double-bevel Japanese kitchen knife, Kai says about 15° per side — “so your little finger just slips under the spine” — and Tojiro says 10–15°, about 7–10 mm between stone and spine. GLOBAL’s rule of thumb: tilt the blade about 15°, “about 1–2 ten-yen coins thick”. Shun sharpens at 16° per side and puts Western knives at 20–25°.^{[66][64][5][67]}
3. Hold the knife at about 45° to the stone’s length, edge toward you, with a three-point grip; press on the push stroke and ease off on the pull, using the whole length of the stone.^[66][64]
4. Keep the slurry. The muddy water (研ぎ汁) contains abrasive and helps the stone cut; add water when the surface dries.^[19][65]
5. Raise a burr. Sharpen until you feel a slight catch (the burr, kaeri) along the whole edge on the other side, then do the other side.^[66][5]
6. Remove the burr with a few light strokes on the finishing stone or by drawing the edge across newspaper, then test-cut.^[66][68]
7. Change grit cleanly. Wash the knife, stone and hands between grits so coarse grit doesn’t spoil the next stone.^[65]

That is the whole whetstone usage tutorial in seven steps. Sharpening tips: keep the angle steady — rocking the knife between push and pull rounds the edge (Tojiro calls this shakuri-togi). Tojiro also warns that sharpening more acute than the factory angle can void its warranty.^[47]

Single-bevel knives (yanagiba, deba)

Lay the bevel flat on the stone up to the shinogi line, raise a burr along the whole edge, then flip the knife and lay the hollow back flat (0°) to remove it.^[19] For beginners, Jikko suggests a #1000 then a #6000, about 10 strokes per section.^[68] Pull-through sharpeners don’t work on single-bevel knives — use a whetstone.^[69]

For the knives themselves, see our Japanese knife brands guide and Japanese chef’s knives buying guide.

How to Flatten a Whetstone (Flattener / Leveling Stone)

Stones wear unevenly and dish in the center, and a stone that isn’t flat won’t sharpen well, so flatten it first.^[70][47] Kai lists three ways: a flattening stone, rubbing two stones of the same kind together, or loose abrasive on wet-dry paper; steel dust collects in the low spots, so you can see where the stone is dished.^[70]

• Shapton Diamond Glass Lapping Plate: for #500 and finer; draw a pencil grid on the stone and rub until the lines disappear. Shapton recommends flattening before every sharpening session and says the plate lasts roughly 1,000–3,000 flattenings.^[71][46]
• Shapton NAORU: a cast-iron plate used with lapping powder (coarse, medium and fine by stone grit); ¥16,390 at Ueda Kanamono.^[72][26]
• Atoma: Tsuboman’s diamond flattening plate, positioned for hard stones.^[55]

Shapton’s Lapping Disc is a dressing stone for clogged surfaces on #2000 and coarser stones.^[25] After flattening, chamfer the corners so they don’t chip or nick the edge.^[65]

Whetstone vs Honing Rod vs Pull-Through Sharpener

Honing realigns a rolled edge and removes no metal; sharpening removes metal to make a new edge, says Shun. Its ceramic rod does remove metal, so use it more sparingly than a steel.^[73] Tojiro does not recommend a steel rod for carbon-steel (hagane) knives because it damages the edge, and calls pull-through sharpeners no substitute for a stone; Kai suggests a bench stone for real resharpening and a pull-through or rod for quick touch-ups.^[74][75][2] How often? Tojiro and GLOBAL suggest a stone once or twice a month; Shun says once or twice a year is often enough for home cooks who hone regularly.^[64][5][73]

How Long Do Whetstones Last, and How to Store Them

King Toishi says “several years or more” in normal home use; Tojiro calls stones consumables.^[21][47] To make them last:

• Rinse off the slurry, then dry the stone in the shade — Kai says 2–3 days until fully dry — before storing.^[76]
• Don’t store a stone wrapped in a wet cloth to save soaking time: Tojiro says it degrades the stone and causes cracks.^[65]
• Keep stones indoors, out of direct sun and away from cold, very dry places; Jikko says magnesia-bond stones crack most easily. Don’t fan-dry Shapton stones.^[77][13][63]

Japanese Natural Whetstones (Tennen Toishi): Types and Sources

Natural stones are graded the same way — coarse, medium and finishing — and vary in quality even from the same source, which is why synthetic stones with consistent grit are now widely used.^[40]

Sources: ^{[40][78][79][80]}. Awase-do (合砥) is the hard, fine finishing stone for razors and blades, and Kyoto’s Narutaki stone is the famous one.^[42] Narutaki stone comes from around Narutaki, Umegahata and Takao in Kyoto; in 1607 the shogunate gave the Hon’ami sword-polishing family mining rights, and the trade peaked from Meiji to early Showa before synthetic stones and power tools cut demand.^[81] Kyoto Prefecture’s Red Data Book lists the whetstone-bearing siliceous shale as a geological site needing attention.^[82] A Kameoka quarry operator says the area once had 30-odd whetstone businesses and only his remains.^[83][84]

• Nakayama: finishing stones from Umegahata; the mine closed decades ago, so good stones on the market are mostly old stock, and a January 2024 magazine piece cited an example at ¥3,300,000. That is why top natural stones are expensive.^[85]
• Amakusa (Kumamoto): Kotobank calls it a coarse sandstone; its maker classes it as a medium stone that can take an edge by itself.^[86][87]
• Tsushima (Nagasaki): a razor-finishing stone.^[88]
• Nagura: very fine tuff from Shinshiro, Aichi, used to dress finishing stones (rubbing it on raises a slurry).^[80]

Natural stones carry no JIS grit number. The Kyoto Whetstone Sales Trade Association (founded 1948, 14 member firms in Kyoto and Shiga) is a starting point for dealers.^[89]

Ceramic and Diamond Whetstones

“Ceramic stone” usually means a vitrified bond: grit mixed with feldspar and clay and fired at 600–1,300 °C — though Tojiro notes that not everything sold as ceramic is made that way.^[61] Very hard steels (Aogami, powdered high-speed steel, HRC 60+) can skate on a hard stone, so a softer stone may suit them; diamond is the hardest abrasive but can be a poor match with carbon steels.^[1][61] Ceramic knives can’t be sharpened on ordinary stones: Tojiro says to use a diamond stone, and Shapton’s stones are not for ceramic blades.^[1][13]

Japanese Whetstones for Chisels and Plane Blades

Joshaburo, a plane maker in Miki, says to flatten every stone first and finish a plane blade at about 28–30°: more acute chips, more obtuse makes the plane heavy to push, softwood takes a sharper angle and hardwood about 33–35°.^[90] Kakuri’s steps for planes and chisels: sharpen the face on the medium stone to a burr, remove the burr on the finishing stone, then finish face and back at roughly a 7:3 ratio.^[91] For the chisels and planes themselves, see our Japanese woodworking tools guide.

How to Buy Japanese Whetstones from Japan

1. Search in Japanese. Whetstone is 砥石; medium stone 中砥石, finishing stone 仕上砥石, combination stone 両面砥石, flattening stone 面直し砥石, natural stone 天然砥石. Add the grit: #1000, #6000.
2. Japanese whetstone kit or starter set? A kit is usually a combination stone (Naniwa Basic), a combination stone on a base (King KDS) or a set of stones with a holder (Shapton 50308); a separate flattening stone completes a sharpening kit.^[6][29][25]
3. Check the listing: grit, size in mm, weight, whether a base or case is included, and the soak rule (吸水 / 水をかけるだけ).
4. Mind the weight. A full-size #1000 stone weighs roughly 0.7–1.2 kg (1.5–2.6 lb); thin Shapton stones are 360–500 g. International shipping is charged on the greater of actual and volumetric weight, so two or three stones in one box usually beat separate parcels — get a quote first.
5. Check maker policies. Naniwa does not sell its Japan-market models abroad, and Sigma Power’s own shop cancels forwarding-service orders; buy from marketplace listings and check each shop’s terms.^[29][54]
6. Before it ships: stones can chip. Add package reinforcement (from ¥100; a box change and outer padding are extra) or unboxing photos (¥500 / ¥700) to check the stone at the Tokyo warehouse.

OneMall buys from Japanese marketplaces such as Mercari, Yahoo Auctions, Rakuten and Amazon Japan, and from other Japanese online stores (including maker web shops) through LinkBuy. Items that need a lottery entry, purchase limit, Japanese identity verification or a merchant account cannot be purchased. International shipping is charged on the greater of actual weight and volumetric weight (length × width × height ÷ 5,000) of the box the warehouse uses.

Service fees are ¥300 per item on most marketplaces; from ¥200 per item on Yahoo Auctions and LinkBuy. The first six orders consolidate free; each additional order costs ¥100. Storage is free for 90 days after arrival (30 days after consolidation). Payment is by Visa, Mastercard or PayPal, settled in USD.

US buyers: since August 29, 2025, US-bound parcels of any value go through customs and pay applicable duties, taxes and fees — the $800 de minimis exemption no longer applies. OneMall currently ships to the United States by ECMS, DHL and Japan Post EMS (DDP — declared value up to USD 2,500, duties prepaid with the shipping fee); the live quote at checkout shows which lines accept your parcel.

If something breaks: damage caused inside the warehouse by OneMall is refunded at the item’s purchase price; damage in international transit is compensated up to the international shipping fee paid, and must be reported within 24 hours with the order number, photos and a full unboxing video. Loss in transit is handled by the carrier, and OneMall helps confirm with the carrier and file the claim within 72 hours. Duties and customs fees are paid by the buyer.

Browse #1000 whetstones, King whetstones, Shapton Kuromaku, Suehiro Cerax or natural whetstones, and compare the best Japan proxy services and proxy costs by total landed cost.

Frequently Asked Questions

What grit whetstone should I start with for Japanese knives?

A #1000 medium stone. King, Tojiro and Kai all describe #1000 (or #800–#1000) as enough for routine sharpening; add a #5000–#6000 finishing stone for a finer edge.

What is a 1000/6000 combination whetstone used for?

The #1000 side sharpens a dull knife; the #6000 side refines the edge. On the King KW-65, start on the brown #1000 side and finish on the pale-yellow #6000.

Do you soak Japanese whetstones?

Depends on the stone: King medium stones about 3 minutes; Shapton and Suehiro Debado are splash and go; never soak Shapton longer than 30 minutes.

What angle should I sharpen a Japanese knife at?

About 15° per side for double-bevel kitchen knives (Kai, GLOBAL); Shun uses 16°. Single-bevel knives are sharpened with the bevel flat on the stone.

Is JIS #1000 the same as 1000 grit sandpaper?

No. JIS #1000 is about 11.5–15.5 µm; FEPA P1000 sandpaper is about 18 µm. Conversions are approximate.

Is Shapton Japanese?

Yes. Shapton makes its stones in Mashiko, Tochigi.

Who makes King whetstones?

King Toishi in Tokoname, Aichi (since 1940); Matsunaga Toishi of Osaka sells them.

Why are natural Japanese whetstones so expensive?

Most of Kyoto’s famous finishing-stone quarries, such as Nakayama, have closed, so many stones on sale are old stock, and quality varies stone by stone.

Can I sharpen a ceramic knife on a whetstone?

Not on an ordinary stone — use a diamond stone.

References

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28. Naniwa Abrasive Mfg., History. https://www.naniwa-kenma.co.jp/company/history/
29. Naniwa Abrasive, Sharpening stones for EU/USA/Canada/Australia. https://www.naniwa-abrasive.com/product/sharpening_stone/index1.html
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31. Rakuten search, Suehiro CERAX 1010. https://search.rakuten.co.jp/search/mall/%E3%82%B9%E3%82%A8%E3%83%92%E3%83%AD+%E3%82%BB%E3%83%A9%E3%83%83%E3%82%AF%E3%82%B9+1010/
32. Sigma Power Corporation (Saicom), Company history. http://www.saicom.info/cgi-bin/saicom/siteup.cgi?category=5&page=1
33. Rakuten search, Sigma Power Select II. https://search.rakuten.co.jp/search/mall/%E3%82%B7%E3%82%B0%E3%83%9E%E3%83%91%E3%83%AF%E3%83%BC+%E3%82%BB%E3%83%AC%E3%82%AF%E3%83%882/
34. Tsuboman, Company profile. http://www.tsuboman.com/company/
35. Akimoto Yukichi Shoten, Atoma for flattening whetstones. https://www.a-yukichi.com/products/detail/5305
36. Homemaking, Atoma for flattening whetstones. https://www.homemaking.jp/products/detail.php?product_id=183502
37. SHOKUBI, King Hyper #1000 soft. https://www.shokubi.jp/shop/g/g101061010/
38. JIS R 6001-2:2017 Bonded abrasives — microgrits (via kikakurui.com). https://kikakurui.com/r6/R6001-2-2017-01.html
39. Fuchioka, Abrasive grit sizes (JIS tables). https://www.fuchioka.co.jp/abrasive/particle/
40. Kotobank, Toishi (whetstone), Heibonsha / Nipponica / Britannica Japan. https://kotobank.jp/word/%E7%A0%A5%E7%9F%B3-102927
41. Suehiro, Gokumyo series. https://www.suehiro-toishi.com/category/high-grade-whetstone/gokumyo-series/
42. Kotobank, Awase-do. https://kotobank.jp/word/%E5%90%88%E7%A0%A5-2004302
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