DMT Dia-Sharp Credit Card Diamond Sharpening Stone (D3EFC): problems, parts and running costs

Checked: 2026-10-19

Summary

A wallet-sized three-grit diamond kit (coarse 45 micron / 325 mesh, fine 25 micron / 600 mesh, extra-fine 9 micron / 1200 mesh) that covers restoring, honing and polishing in one pocketable set, with no oil and no consumables. Owners and DMT frame it as a field and touch-up tool rather than a bench-stone replacement, and there are second-hand reports of warped plates and flaking plating on DMT credit-card sharpeners. The kit costs about $35-37 for the set (DMT direct $36.59, SharpeningSupplies.com $35.07, Oct 2026).

Common problems and fixes

Small plates make big jobs tedious — each plate is only 3-1/4 in. x 2 in., so longer blades and badly damaged edges are harder to work; one owner advises saving for a different setup for home use. [5][12]
Aggressive feel when new — the diamond surface feels aggressive out of the box and smooths after break-in, with no impact on long-term performance; no fix needed. [2]
Not for lapping or flattening — DMT warns its diamond stones should not be used to lap or flatten other stones unless the stone is designated Dia-Flat; use a dedicated flattening stone for that job. [1][2]

Parts and consumables

Single-grit plates (D3C coarse / D3F fine / D3E extra-fine) — $12.99 each at SharpeningSupplies.com (Oct 2026); DMT says diamond stones last several years under heavy daily use and ten or more years for occasional kitchen-knife use, so replacement is rarely needed. [2][3]
No consumables or replacement parts are required by the manufacturer; the plates work dry or with water, so there is no oil to buy. [1][2]

Yearly running cost

None. The kit needs no oil, no replacement plates and no parts; the only recurring spend is cleaning — water after each use and occasionally a mild kitchen abrasive cleanser with a nylon scrub brush. [1][2]

When it is a good buy

DMT direct lists the 3-piece kit at $36.59 (Oct 2026); SharpeningSupplies.com lists it at $35.07 against a $38.97 compare-at, with single grits at $12.99 against $15.79 (Oct 2026). [1][3]
Around $35-37 for three grits, the kit is a sensible travel, EDC and field touch-up tool; the low cost is the main justification for the second-hand warping and flaking risk, so check the plates on arrival. [7]
For home sharpening, one owner says you would be better off saving for a different setup; put the money toward a full-size diamond stone or a guided system instead. [5]