For most people the right DMT is one of two: the Diafold fine/coarse if you want a folding pocket sharpener for knives and tools, or an 8-inch Dia-Sharp or DuoSharp bench stone if you sharpen kitchen knives at a counter. DMT's diamond stones cut fast and stay flat. They also handle hard steels that ordinary stones struggle with. Just don't read their grit names like Japanese grits: DMT's "extra-fine 1200" is a 9-micron diamond, which is a coarser finish than many people expect.
Quick picks
| Best pocket sharpener | DMT Diafold Fine/Coarse (FWFC) | Amazon |
|---|---|---|
| Best bench stone | DMT D8F Dia-Sharp 8-inch Bench Stone (Fine) | Amazon |
| Best two-grit bench stone | DMT 8-inch DuoSharp Plus with Base (Fine/Coarse) | Amazon |
| Best for travel | DMT Dia-Sharp Credit Card Set (3 pack) | Amazon |
| Best for serrated knives | DMT Diafold Serrated Sharpener (FSKF) | Amazon |
| Best for flattening stones | DMT Dia-Flat Lapping Plate (10 x 4 in) | Amazon |
| Best guided kit | DMT Deluxe Aligner Kit (ADELUXE) | Amazon |
How we picked
We searched Amazon for DMT sharpeners on Oct 21, 2026 and sorted the results by what they're for, keeping models with a real owner base. The Diafold fine/coarse showed 100+ purchases last month and 1,398 ratings; the credit-card three-pack showed 200+. Line names and micron figures come from DMT's own site: its FAQ and history page plus the product collection pages, all read the same day. Where an Amazon listing disagrees with DMT, we say so.
This is a How we pick review. We compared DMT's published specs with Amazon listings and owner ratings; we didn't run our own sharpening tests on these stones. How we research.
The DMT lineup, decoded
DMT (Diamond Machining Technology) says it was founded in 1976 and makes its sharpeners in Marlborough, Massachusetts; its site is now run by Acme United. Its FAQ is a little more careful than the history page: most products are made in the US, some US-made stones use imported components, and the EdgeSharp line is fully imported.
| Line | Surface | Shape and size | Use it for |
|---|---|---|---|
| Diafold | Interrupted (polka dot) | Folding handles, 9.5 in open, 5 in closed | Pocket and field sharpening, tool boxes |
| Dia-Sharp bench | Continuous, on a steel plate | 6, 8, 10 and 11.5 in; single or double sided | Kitchen knives, chisels, pointed tools |
| DuoSharp | Interrupted; Plus adds a continuous zone | 8 and 10 in, two grits, with or without base | Bench sharpening, two grits in one stone |
| Dia-Sharp cards and Mini-Hones | Continuous | 3 and 4 in cards, 2.5 in mini-hones | Wallets, tackle boxes, small tools |
| Mini-Sharp | Diamond, keychain size | Keychain | Emergency touch-ups |
| Aligner | Diamond hones on a guide | Clamp and rod kit | Holding a set angle without freehand skill |
| Dia-Flat | HardCoat diamond lapping plate | 10 x 4 in, flat to +/- 0.0005 in | Flattening water stones and oil stones |
Interrupted or continuous?
This is the choice that confuses people most. DMT's polka-dot (interrupted) surface has slightly recessed dots that collect swarf, the steel filings, so they stay off the cutting surface. DMT's continuous surface is solid diamond on steel. DMT says continuous stones are "less aggressive compared to the interrupted," and recommends them for small or pointed tools, which can catch in the dots. For knives, either works. Pick continuous if you also sharpen awls, gouges or drill bits.
DMT grits in microns, and why they aren't JIS grits
DMT labels its stones by color and by mesh, a sieve size for the diamond. The micron number is the one to trust. From DMT's FAQ, with a rough JIS comparison from the JIS R6001 (1973) values in Fine Tools' abrasive comparison chart:
| DMT grade (color) | Diamond size | DMT mesh | Near this JIS grit (by particle size) | Job |
|---|---|---|---|---|
| Extra-extra coarse (silver) | 120 micron | 120 | much coarser than #600 | Heavy repair, flattening |
| Extra-coarse (black) | 60 micron | 220 | coarser than #600 | Chips, axes, mower blades |
| Coarse (blue) | 45 micron | 325 | coarser than #600 | Restoring a dull edge |
| Fine (red) | 25 micron | 600 | between #600 (29) and #800 (20) | General sharpening |
| Extra-fine (green) | 9 micron | 1200 | between #1200 (13) and #2000 (8) | Refining a working edge |
| Medium extra-fine | 6 micron | 4000 | near #2000 to #3000 | Between extra-fine and polishing |
| Extra-extra fine (tan) | 3 micron | 8000 | about #4000 (3) | Final polish |
So a DMT "8000" is closer to a #4000 water stone by particle size, and DMT's fine "600" sits near a #600 to #800 stone, not a #1000. Treat the JIS column as a ballpark. Particle size isn't the whole story: diamond is far harder than the aluminum oxide in a water stone, and owners on Kitchen Knife Forums describe DMT plates as cutting fast and leaving deep scratches for their size. Our sharpening stone grit chart covers the other scales.
The DMT sharpeners worth buying
DMT Diafold Fine/Coarse (FWFC)
The DMT most people own. The handles fold over to cover the diamond, so it rides in a pocket, a pack or a glove box without chewing anything up. The pairing is a working-edge one: coarse to bring back a neglected edge, fine to finish it. For a polished kitchen edge you'd follow it with a strop. Note the Amazon title calls it a "DuoSharp 8-Inch." It isn't. FWFC is DMT's model number for the double-sided Diafold, and the listing's own size (9.5 inches open, 5 closed) matches the Diafold.
- Gritsfine 25 micron (600 mesh) / coarse 45 micron (325 mesh)
- Surfaceinterrupted
- Size9.5 in open, 5 in closed
- Usedry or water
Why it stands out
- Folds closed to protect the plate
- Coarse and fine in one tool
- 1,398 ratings at 4.6 stars
Think twice if
- You want a bench stone for long kitchen knives
- You want an extra-fine finish (look at the extra-fine/fine Diafold instead)
DMT D8F Dia-Sharp 8-inch Bench Stone (Fine)
An 8 by 3 inch slab of continuous diamond on steel, heavy enough to stay put on four rubber feet. That width gives a chef's knife room to sweep, and the continuous surface handles small pointed tools that the polka-dot plates can snag. It has 1,139 ratings. Single grit means one job: maintaining an edge that isn't badly damaged. Pair it with the coarse D8C for repairs or the extra-fine D8E for a finer finish.
- Gritfine 25 micron (600 mesh)
- Surfacecontinuous
- Size8 x 3 x 0.38 in
- Feet4 non-skid rubber
- Usedry or water
Why it stands out
- Stays flat and heavy on the counter
- Continuous surface for pointed tools
Think twice if
- You want two grits in one stone
DMT 8-inch DuoSharp Plus with Base (Fine/Coarse)
Two grits, a base that lifts it off the counter, and both of DMT's surfaces on one stone. The listing describes the recessed polka-dot surface for knives with a small continuous zone at one end for pointed tools, which is DMT's DuoSharp Plus design. With 673 ratings at 4.6 stars, it's the best-reviewed DuoSharp we found. If you'd rather skip the base, the WM8FC DuoSharp Plus is the same grit pair as a bare stone.
- Gritscoarse (blue) / fine (red)
- Surfaceinterrupted plus a continuous zone
- Baseadjustable sharpener base included
- Usedry or water
Why it stands out
- Coarse and fine on one 8-inch stone
- Base included
- Continuous zone for small tools
Think twice if
- You only need one grit
DMT Dia-Sharp Credit Card Set (3 pack)
Three thin diamond cards that fit in a wallet, each in its own color-coded sleeve. They're too small for a chef's knife, but for a pocket knife, a broadhead or a fishhook they're a full coarse-to-extra-fine progression that weighs next to nothing. It was the best-selling DMT in our search at 200+ a month.
- Gritscoarse 45, fine 25, extra-fine 9 micron
- Size3.25 x 2 x 0.05 in each
- Surfacecontinuous
- Casecolor-coded vinyl
Why it stands out
- Three grits in wallet size
- Continuous surface
Think twice if
- Your main knives are long kitchen blades
DMT Diafold Serrated Sharpener (FSKF)
A tapered diamond cone in the same folding handles, small enough at the tip to fit the scallops on a steak knife and wide enough at the base for a bread knife. DMT's listing adds that it doubles as a gut-hook sharpener. Our serrated knife sharpener guide compares it with the Sharpmaker.
- Shape4 in cone, 1/4 to 1/16 in
- Gritfine 25 micron (600 mesh)
- Size9.5 in open, 5 in closed
- Usedry or water
Why it stands out
- One cone covers many scallop sizes
- Folds closed
Think twice if
- You have big bread-knife serrations only (DMT suggests its Diamond Steel for those)
DMT Dia-Flat Lapping Plate (10 x 4 in)
Not a knife sharpener. This is the plate for keeping water stones flat, and DMT says its regular stones aren't meant for that job. DMT sells two Dia-Flats: 120 micron for stones of 1000 grit and coarser, and 95 micron for finer stones. This Amazon listing describes the 95 micron version; check the listing title and photos before you buy if you need the 120. Use it under running water and never over a garbage disposal, per DMT. How to do the job is in how to flatten a whetstone, and alternatives are in our flattening stone picks.
- Size10 x 4 in, 40 sq in
- SurfaceHardCoat diamond
- Grit (listing)95 micron / 160 mesh
- Flatness (DMT)+/- 0.0005 in
Why it stands out
- Flat to half a thousandth, per DMT
- Large 40 square inch surface
Think twice if
- You only own diamond plates (they don't need flattening)
- You sharpen a few times a year (a cheaper plate will do)
DMT Deluxe Aligner Kit (ADELUXE)
A clamp and guide rod that hold the angle while you work three diamond hones. DMT's FAQ lists seven settings, 16 to 40 degrees in 4-degree steps, measured on a 1-inch-wide blade, and notes the angle gets steeper as you extend the rods. That "on a 1-inch blade" matters: a wider or narrower knife lands at a different real angle, so check with a marker. For a full comparison of clamp systems, see best sharpening systems.
- Honescoarse, fine, extra-fine diamond + serrated sharpener
- Guide7 angles (DMT FAQ)
- Usedry or water
- Includesfabric storage pouch
Why it stands out
- Three grits plus a serrated hone
- No freehand skill needed
Think twice if
- You want precise, repeatable degrees across different blade widths
Which DMT for which job
| You want to | Buy | Why |
|---|---|---|
| Keep a pocket or hunting knife sharp anywhere | Diafold FWFC | Folds, two working grits |
| Refine a pocket knife edge on the go | Diafold extra-fine/fine | 9 and 25 micron |
| Sharpen kitchen knives at the counter | D8F Dia-Sharp or DuoSharp Plus | 8 in long, heavy or on a base |
| Repair chips, axes, mower blades | D8X Dia-Sharp extra-coarse | 60 micron removes steel fast |
| Carry sharpening in a wallet | Credit card 3 pack | Three grits, 0.05 in thick |
| Sharpen small tools in a tackle or tool box | Mini-Hone kit (D2K) | 2.5 in hones, three grits |
| Keep a keychain sharpener | Mini-Sharp fine (F70F) | Keychain size |
| Sharpen ceramic knives | Fine Dia-Sharp or Diafold | Diamond cuts ceramic; see how to sharpen a ceramic knife |
| Flatten water stones | Dia-Flat | Made for it; DMT's FAQ steers flattening to Dia-Flat |
If you're weighing DMT against other brands of plate, the best diamond sharpening stone roundup ranks them together. If you're deciding between diamond and water stones at all, start with whetstone vs diamond stone.
How to use a DMT stone
Everything here is from DMT's FAQ:
- Clean the knife first. Grit and food on the blade end up on the stone.
- Use it dry or with a little water. No oil needed.
- Use light pressure. A new diamond stone feels aggressive; DMT says the first few sharpenings are a break-in and it smooths out without losing performance. Pressing hard just tears diamond off.
- Hold a steady angle. DMT suggests about 20 degrees and says a constant angle matters more than the exact number. Their practice tip is the marker method, the same one in our sharpie trick guide.
- Rinse with water and wipe dry after each use. Every few sessions, scrub with a mild kitchen abrasive cleanser and a nylon brush, then store it dry. Keep paper or cloth between stacked bench stones.
DMT replaces stones with defects in materials or workmanship regardless of age, but normal wear isn't covered, and neither is industrial use or abuse.
Who should skip DMT
If you only sharpen soft German kitchen knives and want a mirror-polished edge, a 1000/6000 water stone gives you more finish for the money. DMT's finest common grit, the 3-micron extra-extra fine, sits around a #4000 water stone. Everyone else, especially anyone with hard pocket-knife steels, axes or a stack of water stones that needs flattening, will get years out of a DMT. Start with the Diafold FWFC if you carry a knife and the D8F if you cook.
Sources: DMT, FAQ, history, Dia-Sharp, DuoSharp, Diafold and lapping pages; Fine Tools, comparison of abrasive grain sizes (JIS R6001, 1973); Kitchen Knife Forums diamond stone survey thread. Read Oct 21, 2026. Product details from Amazon listings checked the same day. How we research · Affiliate disclosure