DMT W250CXNB DuoSharp Double: Review, Pros & Cons

Summary

A 10-inch double-sided diamond bench stone with a coarse (45 micron, 325 mesh) face and an extra-coarse (60 micron, 220 mesh) face, sold without a base. It sets bevels and repairs damaged edges fast but does not finish an edge, so plan on a finer stone too; check the suffix, since “NB” means no base.

Strengths

10 x 4 in working surface, about 87% more than the 8-inch model.
Coarse and extra-coarse faces cut fast for bevel setting and chip repair.
Diamond abrasive needs no oil; use dry or with water.
Made in USA; warranty replaces defective units regardless of age.
Flat precision surface claimed to +/- 0.001 in.
Simple upkeep: rinse, dry, store dry.

Weaknesses

Coarse/extra-coarse only; it will not leave a finished edge.
Ships without a base; bench stability costs extra.
No independent instrumented test of this exact model exists.
Rust can collect if stored damp.
SMKW lists it at $185.99 out of stock, above two US sellers.

Verified specifications

Model	DMT W250CXNB, part number W250CXNB; KnifeCenter SKU DMTW250CXNB; UPC 017042003838.
Form	double-sided diamond bench stone, precision flat, two diamond-surfaced sides.
Dimensions	10 x 4 x 0.375 in (250 x 100 x 10 mm).
Grit side 1	coarse, 45 micron / 325 mesh; DMT color code blue.
Grit side 2	extra coarse, 60 micron / 220 mesh; DMT color code black.
Abrasive	monocrystalline diamond on an interrupted “polka-dot” sharpening surface.
Lubrication	no oil needed; sharpen dry or with water.
Country of origin	made in USA.
Base	not included; the DuoBase accessory (part DMTB8250) is a separate purchase.
Surface flatness	DMT’s grit text states +/- 0.001 in on its bench stones (general text, not model-specific).
Intended uses	shears, cleaver and specialty knives, plane sole, machete.
Weight	1.45 lb (KnifeCountryUSA); shipping weight 1.5 lb (KnifeCenter).
Included	the stone and a non-skid mat; no base, no case documented.

Full research notes and sources

Sharpening range: bevels and repair, not finishing

Both faces are coarse. DMT’s published grit ladder runs from extra-extra coarse (120 micron, 120 mesh) through extra coarse (60 micron, 220 mesh), coarse (45 micron, 325 mesh), fine (25 micron, 600 mesh), extra fine (9 micron, 1200 mesh) to extra-extra fine (3 micron, 8000 mesh). The coarse/extra-coarse pair is for setting bevels and repairing damaged edges; it will not leave a great finished edge, so a fine/extra-fine stone is needed to finish. Buying this as a complete sharpening solution wastes the money. The interrupted polka-dot surface removes swarf and is reported by one owner as less aggressive than DMT’s continuous DiaSharp surface; that is a single opinion, not a measurement.

The stone ships without a base. KnifeCenter tells buyers to add DMT’s DuoBase accessory (part DMTB8250) at purchase, and the retailer copy notes a non-skid mat is included. One seller’s overview describes a non-skid rubber base as included, which conflicts with the no-base designation on two other listings for the same part number; assume no base in the box. No sheath or case is documented for this part. Prices read 2026-10-22: KnifeCenter $136.95 against an MSRP of $181.99; Cutlery Shoppe $134.90 from $179.99; SMKW $185.99, out of stock; KnifeCountryUSA $150.32 from a list price of $204.52; the DMT brand site $179.99, marked sold out; the authorized DMT online store from $179.99. The base-equipped version, W250CX-WB, lists at $191.79 and is priced at $143.85 on sale. At about $135 the stone is fairly priced for the coarse side of a bench setup; at $185.99 and up it is poorly priced against two US sellers already undercutting it. The Canadian listing at $249.00 is a different market.

Maintenance, durability and warranty

Diamond surfaces need no oil. DMT’s FAQ adds a break-in period during which the surface feels aggressive, plus cleaning and dry storage requirements; mineral oil or WD-40 used in excess can impede sharpening and damage the sharpener over time. When used properly, kept clean and stored dry, DMT diamond sharpeners last several years; frequent daily use may need replacement in a few years, occasional kitchen use may last ten or more years, and some customers report 20 years of service. Warranty is defect-based: DMT replaces a unit regardless of age if it fails due to defects in materials or workmanship, with normal wear, industrial use, abuse, misuse or neglect excluded. No service parts or re-diamonding service were found for this stone.

Is it worth it?

At about $135, the W250CXNB is a good buy for the coarse side of a bench setup: a large, flat, fast-cutting surface, made in the USA, with a defect-based warranty. It is not a one-stone solution, it does not include a base, and its independent test record is thin. Above $180 the value drops, since two US sellers already undercut that level. Buyers who want a finished edge need a finer stone too; buyers who want a stable bench setup need the DuoBase.

Which model this is

This page covers the DMT 10-inch DuoSharp Bench Stone in the Coarse/Extra-Coarse combination, part number W250CXNB, sold without a base. “NB” stands for no base; the same stone with a base is part W250CX-WB. Identifiers: SKU DMTW250CXNB and UPC 017042003838. The suffix matters because some listings describe a base as included while others for the same part number say no base. Do not confuse it with the 8-inch DuoSharp/Plus stones (WM8CX, W8CXNB, W8CX-WB) or other DMT benchstone series. The Amazon listing for this stone is ASIN B00004WFUL.