FEPA vs JIS vs Mesh: How Sharpening Grit Numbers Compare, and Why to Buy Microns
FEPA vs JIS vs Mesh: How Sharpening Grit Numbers Compare, and Why to Buy Microns - A step into the workshop.
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The shop is warm by mid-morning now, and the honing water goes flat and slick, so I change it twice through a session. It is still the pleasantest sharpening of the year. Door propped open, low light across the bench by seven in the evening, the small snick of a bevel finding the stone and staying there. My grandfather's carving roll holds handles worn to the shape of a grip that was not mine, and the only reason those tools still cut is that three generations of hands kept putting them back on abrasive.
What has changed since his day is not the stones. It is the numbers printed on them.
Set a European-marked 600 beside a Japanese 1200 and every instinct says the second is twice as fine. It is not. As near as the published standards allow anyone to say, they are the same stone. That is not a rounding error and it is not a marketing liberty. It is what happens when four separate documents, written by four separate bodies, all decided to call their output "grit."
Where the Scales Part Company
At the coarse end there is no argument. Lee Valley Tools publishes a chart covering five standards at once, and at 60 grit they land nearly on top of each other: CAMI 60x at 268 microns, FEPA P60 at 269, JIS J60x at 269. If you are hogging a hollow off a chipped iron, the number on the box is honest in any language.
The trouble starts around 220, and Steve Bottorff, writing at silversmithing.com, gives the mechanical reason. Grits of 220 and coarser are graded by sieving. Finer grits are graded by sedimentation. A sieve sorts by whether a grain falls through a hole; sedimentation sorts by how fast a grain sinks through a fluid. Two physics, two tolerance regimes, no shared anchor once the sieve stops being useful. metallography.org marks the same threshold at roughly 240.
Below that line the scales drift apart, and they drift at different rates. Lee Valley's illustration is the one worth keeping in your head: in the 5 to 7 micron range, FEPA paper reads 5000x, ANSI reads 1000x, and FEPA-F reads 800x. One particle size, three labels, a factor of six between the outer two. Sharpening lives entirely inside that band.
A European 600 and a Japanese 1200 Are the Same Stone
The two standards that matter for bench stones are FEPA-F, the European system for bonded abrasives, and JIS 6001, the Japanese one. Both are published as tables of microns, and both are reproduced by manufacturers who have no reason to flatter anybody. GNP Graystar prints FEPA Standard 42.2:2006, Table 1. Resonac, formerly Showa Denko, prints the JIS 6001 micro grain size table. Lay them side by side by particle size rather than by number and the relationship comes clear.
| FEPA-F grade | FEPA-F median (GNP Graystar) | JIS grade | JIS median (Resonac) |
|---|---|---|---|
| F 320 | 27.7–30.7 µm | #400 | 28.0–32.0 µm |
| F 600 | 8.3–10.3 µm | #1200 | 8.7–10.3 µm |
| F 800 | 5.5–7.5 µm | #2000 | 6.1–7.3 µm |
| F 1000 | 3.7–5.3 µm | #3000 | 3.5–4.5 µm |
| F 1200 | 2.5–3.5 µm | #4000 | 2.6–3.4 µm |
F600 on GNP Graystar's FEPA sheet and JIS #1200 on Resonac's are near-exact band matches. So are F1200 on the same FEPA sheet and JIS #4000 on the same JIS table, two labels a factor of 3.3 apart describing the same dust. The rule of thumb, at the fine end where you actually care, is that the European number runs to roughly half the Japanese one for the same cut. Knivesandtools' chart agrees in direction and close enough in value, putting JIS 1,000 at FEPA-F 550 and 12 microns.
Knivesandtools also makes the measurement-theory point better than I can. Microns are a ratio measurement with absolute values behind them. Grit numbers are nominal, labels without units, which is why a 16,000 grain is not necessarily half the size of an 8,000 one. The number is a name, not a quantity.
The Number Is a Crowd, Not a Grain
Even inside one standard, a grit number is not a size. It is a permitted distribution, and the primary tables spell out how loose that permission runs.
Resonac's JIS table gives #1000 a median of 10.5 to 12.5 microns, and a maximum permitted particle, ds-0, of 32 microns. Three times the median, entirely in spec. At #8000 the median is 0.9 to 1.5 microns with a ds-0 ceiling of 6.0. GNP Graystar's FEPA sheet is the same story from the other side: F1000 has a median of 3.7 to 5.3 microns, and its coarsest three percent may run to 10.
Read that median band again. Two stones can both be honestly labelled F1000 while one sits at 3.7 microns and the other at 5.3. That is a 43 percent difference with nobody cheating. It is also the best explanation I know for why two stones bearing the same number from two makers leave scratch patterns you can tell apart by eye. Sharpening Supplies built a proprietary 1-to-10 level chart around the problem, saying plainly that one company's "fine" might be another manufacturer's "coarse."
Where the Standard Stops, and Arithmetic Takes Over
Resonac's JIS 6001 micro grain table ends at #8000. There is no #10000 row, no #16000, no #30000. Fine Tools says the same thing without softening it: in Japan, abrasive grains are standardised only up to grit 8000, and everything above that is factory standards, where one can only trust the manufacturer. Zen-Wu Toolworks, which maintains a micron-spined reference table, marks its own values beyond the defined ranges as uncertain, because no standard defines those grades.
Which brings me to the most instructive column of numbers in this whole business. Sharpening Supplies publishes micron ratings for the full Shapton GlassStone HR line, fourteen grits deep. Divide 14,700 by the grit number and you get the published micron figure. Every time. 1000 grit, 14.7 microns. 8000 grit, 1.84. 30000 grit, 0.49. Fourteen for fourteen, to the reported decimal place. Shapton has not said this is what they do; it is arithmetic anyone can run on the retailer's own page. But fourteen independent particle measurements do not land on a clean constant. That is an extrapolated scale, and it reaches below #8000 as well as above it.
The formula does not agree with JIS, either. Shapton's "1000" at 14.7 microns is coarser than the JIS #1000 band of 10.5 to 12.5, sitting instead where JIS puts #800. Shapton's "8000" at 1.84 microns is above Resonac's JIS #8000 band of 0.9 to 1.5, nearer JIS #6000. And Sharpening Supplies lists three Shapton 30,000-grit stones at three different ratings: .48 microns for the Kuromaku Professional, .49 for the HR Glass Stone, .44 for the Glass Stone Seven. One maker, one number on the box, three answers.
Mesh Plays a Fourth Game
Diamond plates are sold on mesh numbers, which are a different fiction again. DMT's colour-coded chart, published via Sharpening Supplies, gives both mesh and microns, and checking one against the other is illuminating. The green Extra Fine is 9 microns at "1200 mesh," and JIS #1200 is 8.7 to 10.3 microns. Essentially exact.
The tan Extra-Extra Fine is 3 microns at "8000 mesh." JIS #8000 is 0.9 to 1.5. DMT's plate is two to three times coarser than a Japanese 8000 waterstone, and by particle size it belongs at JIS #3000 to #4000. If you finish on that plate believing you have reached 8000, you have stopped considerably short of it. The micron figure on the same plate told you the truth the whole time.
Atoma, also via Sharpening Supplies, is more honest again, publishing ranges: 400 grit at 37 to 44 microns, 600 grit at 30 to 40. Those overlap. Two numbers from one maker, and they do not cleanly separate the products.
What to Buy, and What to Ask Before You Do
Buy the micron figure. Where a maker publishes one, you have something you can compare across brands, materials and continents. Where a maker publishes only a number, you are buying a word.
Christopher Schwarz made this argument at Lost Art Press in 2014 and gave his protocol in microns rather than grits: grinding at 50 microns or larger, honing from 15 down to 6, polishing under 6 and finishing near 1. That is a specification you can shop against. Lee Valley's diamond pastes are sold exactly that way, 1, 3 and 6 micron at $18.90 a syringe or $52.50 for the set, with no grit number anywhere on the listing.
Against that, consider what the number alone costs. Sharpening Supplies lists the Naniwa Chocera Pro 10000 at $275.00, with no micron rating and no stated grit system on the page. Lie-Nielsen's Ohishi combination stone at $90.00 is likewise sold on grit numbers with no microns published. Inside the Shapton HR line, moving from the 16000 at 0.92 microns and $134.10 to the 30000 at 0.49 microns and $324.00 costs $189.90 for 0.43 microns of refinement, both figures produced by dividing a constant by a label in a range where no standard exists to check them. And the same day, the DMT D8EE, 3 micron, was $129.99 on DMT's own site and $96.99 at Woodcraft. Same plate, same week, $33.00 apart. Those prices came off live pages on 27 July 2026, single-retailer snapshots.
Microns are necessary. They are not sufficient. Zische points out that bond type governs how a grain actually cuts, and Schwarz adds that natural products are difficult to rate this way. My grandfather's oilstone has no number on it and never did, and it still hones a paring chisel to something that will pare.
So ask the seller for microns before you ask anything else, and if the answer is a four-digit number and a shrug, buy the plate that prints its particle size on the box. Then stop worrying about the top of the range. The edge you can feel with a thumbnail was decided somewhere between 15 and 1 micron, and everything above that is a number a factory chose.