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Diamond Machining Technology (DMT) Dia-Sharp Diamond Sharpening Stone Credit Card

Diamond Machining Technology (DMT) Dia-Sharp Diamond Sharpening Stone Credit Card

By Diamond · Knife Sharpening · Kitchen & Cooking

  • Each stone measures 3-1/4 in. x 2 in. x 0.05 in.
  • Micronized monocrystalline diamond surface on a steel plate
  • Sharpens dry or with water
  • Model D3EFC
  • Made in the USA

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Problems, parts and running costs

Summary

A wallet-sized three-grit diamond sharpening kit from DMT that covers coarse, fine and extra-fine in one pocketable set. It suits field touch-ups and quick edge work; check the small plate size before you buy, since it is not a bench-stone replacement.

Strengths

  • Three grits cover restoring, honing and polishing in one pocket-sized set.
  • Each plate is a solid steel blank with a continuous diamond surface, heavier than DMT’s resin lines.
  • Usable dry or with water, so there is no oil to carry or clean up.
  • Color-coded vinyl cases keep the grits sorted and pocketable.
  • DMT backs it with an age-independent defect replacement guarantee.
  • Owners report it is cheap, pocketable and capable of getting softer steels shaving sharp with practice.

Weaknesses

  • The small plate makes longer blades and badly damaged edges more tedious to work.
  • It is a field/touch-up tool, not a home sharpening system; one owner advises saving for a different setup.
  • DMT warns these stones should not be used for lapping or flattening other stones.
  • Second-hand reports describe DMT credit-card plates arriving warped or with plating that flaked off.
  • No credible instrumented test of this exact model was found, so measured performance is unverified.
  • The diamond surface feels aggressive when new and smooths only after break-in.

Verified specifications

Contentsthree separate diamond plates — coarse, fine and extra-fine — in one kit, SKU D3EFC.
Coarse grit45 micron / 325 mesh (blue).
Fine grit25 micron / 600 mesh (red).
Extra-fine grit9 micron / 1200 mesh (green).
Abrasivemicronized monocrystalline diamond bonded to a flat steel plate.
Dimensions3-1/4 in. × 2 in. × 0.05 in. per plate.
Shipping weightsingle plate 68 g (0.1499 lb); three-pack 158 g (0.3483 lb).
Usedry or with water; no oil needed.
Includedgrit color-coded vinyl carry cases.
Originmade in the USA.
Warrantydefect guarantee that replaces the product regardless of age, excluding normal wear, industrial use, abuse, misuse or neglect.
Full research notes and sources

Grits and what each is for

DMT groups the set into three stages. The coarse 45 micron / 325 mesh plate brings back a dull edge, the fine 25 micron / 600 mesh plate hones it, and the extra-fine 9 micron / 1200 mesh plate polishes. Each plate is 3-1/4 in. × 2 in. × 0.05 in., with a micronized monocrystalline diamond surface on a flat steel blank, and it works dry or with water. The kit ships with grit color-coded vinyl cases: blue for coarse, red for fine, green for extra-fine.

Field use and limits

The clearest owner signal is that this is a field/touch-up sharpener rather than a home system. One r/knifeclub owner keeps some “for field sharpening, not bad”; another says that with a “$10 dmt credit card sharpener and a strop I can get softer steels like sandvik and 440C shaving sharp” given practice. A broader DMT thread notes the interrupted-surface plates feel “actually pretty good” and avoid the bumpy feel of some other diamond plates. But at least one owner says that for home use you would be better off saving for a different setup, and the small surface makes larger blades and heavily damaged edges harder to work.

Care, cleaning and how long it lasts

DMT says diamond sharpeners do not last forever but last several years under heavy daily use, and ten or more years for occasional kitchen-knife use, with some customers reporting 20 years of service. Clean the plate after each use with water and wipe it dry; periodically use a mild kitchen abrasive cleanser with a nylon scrub brush. DMT recommends dry or water only. Mineral oil or WD40 will not harm the product but can impede sharpening if used in excess and can damage it over time if not cleaned off. If performance drops, clean the stone first and test for remaining diamond by rubbing it on an old glass jar.

The manufacturer lists the three-piece kit at $36.59. A US specialty retailer lists the D3EFC three-pack at $35.07 against a $38.97 compare-at, and each single grit at $12.99 against $15.79. There are no consumables or replacement parts; the only running cost is cleaning supplies.

Is it worth it?

For a travel, EDC or quick touch-up tool, the low price is the main thing that justifies the risk, especially with the second-hand reports of warped plates and flaking plating. If you want to do real sharpening at home, put the money toward a larger stone or a guided system instead.

Which model this is

This page covers the DMT 3-in. Dia-Sharp Credit Card Sharpener, Extra-Fine, Fine and Coarse kit, manufacturer SKU D3EFC. The same sharpener is also sold as separate single-grit items with their own SKUs: D3C coarse, D3F fine and D3E extra-fine. The Amazon listing is ASIN B00006IIO3.

Sources

Manufacturer:

Independent reviews:

Owner reports:

Buying guides for this category

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