Diamond sharpening stones — the complete DMT guide (2026)

A sharp chisel splits the wood — a dull one tears it. Over a couple of decades the diamond sharpening stone has gone from specialist tool to standard kit in Swedish joinery workshops, and DMT is the name behind that shift. This guide walks through the entire DMT Diasharp range at Ernst P, the colour-code system, grit selection for different edges and the technique you need to get the most out of your diamond sharpening stone.

What is a diamond sharpening stone?

A diamond sharpening stone is a flat steel plate where industrial diamonds are electrolytically bonded in a nickel matrix onto the sharpening surface [1][2]. Unlike traditional sharpening stones (oil stones, waterstones, ceramic stones) where the grains are held in a brittle binder that wears away during use, the diamonds on a diamond sharpening stone are mechanically and chemically locked into the metal surface.

That gives three decisive advantages:

1. The stone stays flat. A waterstone has to be flattened frequently because the surface becomes uneven. A diamond sharpening stone never needs flattening.
2. Faster stock removal. Diamond is the hardest known material (10 on the Mohs scale) and cuts steel faster than ceramic or aluminium oxide.
3. Works both dry and wet. No soaking, no honing oil that hardens.

The diamond surface also has a built-in hole pattern (the interrupted surface on the Diasharp range) that collects swarf during sharpening so you do not grind on your own filings.

DMT — American manufacturer since 1976

Diamond Machining Technology (DMT) was founded in 1976 in Marlborough, Massachusetts, and has since specialised exclusively in diamond-based sharpening tools [1][3]. They still manufacture everything in the USA and are considered the market leader in diamond sharpening stones — their Diasharp range is the industry standard among knife makers, surgeons, woodworkers and culinary professionals worldwide.

DMT's own patented process electrolytically bonds the diamond grains to nickel-plated steel plates so the diamond grains protrude above the surface rather than being fully embedded. That gives a more aggressive cut without clogging.

DMT's colour-code system — the foundation you must know

The entire DMT range is built on a simple colour-coding system. Same colour = same grit size, regardless of format. Learn the chart once — then you can read the whole DMT catalogue [1][2]:

Product-code logic: the letter in the article number matches the colour. D8F = 8-inch Fine (red). D3E = 3-inch Extra fine (green). D8EE = 8-inch Extra Extra fine (light green/tan). As soon as you can read the code, you know exactly which stone it is.

Mesh and micron — how the conversion works

Mesh is the number of threads per inch in the sieve the grains were sorted through. Higher mesh = finer grit.

Micron (µm) is the actual grain size in thousandths of a millimetre. Lower micron = finer grit.

The two scales run in opposite directions: 220 mesh = 60 µm (coarse) while 8000 mesh = 3 µm (very fine). The correlation is not linear but logarithmic — doubling the fineness usually requires four times the mesh number.

Size ranges in the DMT catalogue

DMT makes the same colour codes in different physical formats. The choice comes down to where you sharpen and what you sharpen on:

D8 — 8-inch Diasharp bench stone (200 × 65 mm)

The classic bench format. Long enough to sharpen the entire bevel of a plane iron in a single stroke. Sits on the bench or in a sharpening cradle (non-slip base).

D8F (Red / Fine, 600 mesh) — the best-selling D8 stone. A working edge for chisels, plane irons, hand axes and knives. If you are only buying one diamond sharpening stone: buy this one.

D8EE (Extra Extra Fine, 8000 mesh) — the ultimate finish. For carving tools, straight razors, Japanese knives and the final polish before the working edge goes into service. Used after D8F and a Green (E).

D3 — 3-inch mini in credit-card format (75 × 50 mm)

Field stone. Fits in the toolbox, pocket or hunting bag. Same diamond quality as the D8 — just a smaller surface.

D3F (Red / Fine) — touch-up for knife edges and pocket knives in the field. Complements the D8 in the workshop.

D3E (Green / Extra Fine) — fine honing of a fine edge when you are away from the bench.

D3C (Blue / Coarse) — coarse sharpening in a minimal format. For restoring dull edges when you are travelling or out in the woods.

W7 — 7-inch handheld Whetstone

The format between D3 and D8. Big enough for steady sharpening, small enough to hold in the hand while sharpening against the knife edge.

W7E (70 mm Extra Fine / Green) — a popular size for knife sharpening using a handheld technique.

F70 — 70 mm compact field stones

Narrow stones optimised for knife edges and handheld sharpening in the field. Practical for hunting and outdoor use.

F70E (Extra Fine / Green) — fine sharpening of hunting knives.

F70C (Coarse / Blue) — coarse sharpening and restoring dull knife edges.

A4 — Aligner 111 × 23 mm for sharpening jigs

Narrow format designed for knife-sharpening jigs such as Lansky, DMT Aligner and other angle-controlled systems. The narrow format (23 mm) fits the jig's clamp.

A4X (Extra Coarse / Black) — reprofiling damaged edges in a jig.

A4E (Extra Fine / Green) — fine sharpening with angle control in a jig.

Use on chisels and plane irons

A new chisel from the factory rarely has a perfectly flat bevel. Before first use it should be flattened on the back and sharpened to the correct bevel angle (25-30°).

Progression for a new chisel or plane iron:

1. Flatten the back on a D8F (Red) — only the outermost 10-20 mm at the edge needs to be mirror-flat. Lay the iron flat on the stone, back down, and sharpen until the whole surface is evenly polished.
2. Coarse sharpen the bevel on a D8C/Blue 325 (or D8F if the bevel is already roughly correct) — hold the iron at 25-30° against the stone and push forward. The goal is an even new bevel with no secondary angle.
3. Fine sharpen on the D8F (Red, 600 mesh) — same angle, lighter pressure.
4. Polish on the Green (E, 1200 mesh) and optionally the EE (light green, 8000 mesh) for a razor-sharp edge.
5. Deburr on the back — draw the back flat across the Green stone a few times to remove the burr.

A chisel you use daily usually only needs steps 3-5 as maintenance sharpening once a week. Coarse (Blue) is only used when the edge is damaged or when you change the bevel angle.

Use on knives

For kitchen knives, hunting knives and pocket knives, Red and Green are usually enough. Dull and damaged edges need Blue or Black.

Progression for a regular knife:

1. Coarse/Blue if the edge is really dull or chipped.
2. Fine/Red to set a new working edge. Angle 15-20° for a kitchen knife, 20-25° for a hunting knife, 10-15° for a straight razor.
3. Extra Fine/Green for fine honing and finish.
4. Stropping on leather (not a DMT stone) as a final finish if you wish.

For straight razors and Japanese knives, the D8EE (8000 mesh) is a worthy last stone before the strop.

Technique — how to sharpen correctly

The angle

Chisels and plane irons: 25-30° bevel angle. 25° for soft wood, 30° for hardwood and chisels struck with a mallet.

Kitchen knives: 15-20° per side (30-40° total angle).

Hunting knives and outdoor knives: 20-25° per side.

Straight razors: 10-15° per side.

An angle guide (honing guide) such as a Veritas or Eclipse is the easiest way to hold a constant angle on chisels. For knife sharpening without a jig — place a coin with the same thickness as the correct angle under the edge, or use DMT's own Aligner jig with the A4 stones.

Dry or wet?

DMT Diasharp tolerates both [4]. The differences:

• Dry: fast, no mess, works for a touch-up. But swarf builds up on the stone and reduces aggressiveness. Brush off the swarf often.
• Water: flushes the swarf away, sharpens more evenly, less dust. Recommended for longer sharpening sessions. A drop of washing-up liquid in the water helps (surface tension).
• Honing fluid (DMT's own): lubricates without hardening, perfect for the fine stones.

Never use oil-stone oil (Norton, Camellia) on a diamond sharpening stone — it clogs the matrix.

Pressure and motion

Diamond cuts best with light pressure. Hard pressure does not give faster sharpening — only wear on the diamond grains. Use the weight of the iron/knife plus light finger pressure.

The motion should be long and even — draw the entire edge across the whole surface of the stone in each stroke. That wears the stone evenly and gives an even edge. Never sharpen only in the middle of the stone.

Cleaning and maintenance

After every use:

1. Rinse under running water.
2. Scrub gently with a nylon brush or toothbrush — never a wire brush.
3. Wipe dry with a towel.
4. Store dry, preferably in the original packaging or in a box free from moisture.

For heavier cleaning (clogged with metal swarf): warm water + washing-up liquid, or DMT's own diamond-stone cleaner. Scrub gently.

Avoid:

• A wire brush (damages the nickel matrix).
• The dishwasher (heat + salt corrode the steel plate).
• Abrasives/polishing compounds (fill the pore structure).
• Solvents (petrol, acetone — can dissolve the nickel matrix over time).

Service life — how long does a diamond sharpening stone last?

A well-cared-for DMT Diasharp stone lasts for decades. Diamond grains do not wear away like ceramic and aluminium oxide — they are the hardest material in existence. Things that can shorten the service life:

1. Initial "break-in": new diamond sharpening stones often feel most aggressive during the first 10-15 uses. After that they settle down and cut steadily for many years.
2. Mechanical damage: drops on the floor, bending, falling tools that strike the surface can dislodge individual grains.
3. Corrosion of the steel plate: if the stone is left wet, the steel under the matrix can start to rust. Always wipe dry after use.

For hobby use on evenings and weekends: count on 15+ years. In daily professional use (a joiner sharpening chisels five times a day): 5-10 years before the aggressiveness starts to drop.

Why multiple grits?

Same principle as sandpaper: do not skip more than one grit step. If you start with Red (600 mesh) on a really dull iron, you will sharpen for hours. Start with Blue (325 mesh) and you create a new edge in 5 minutes — and finish on Red to remove the Blue scratches.

Minimum setup: two stones, Red (working edge) + Green (finish). Covers 80 % of all maintenance.

Complete setup: Black (reprofiling) + Blue (coarse) + Red (fine) + Green (extra fine) + EE (ultra finish). Five stones that cover everything from a catastrophically damaged edge to straight-razor sharpness.

Recommendation for the Swedish workshop:

• D8F (Red) — the bench workhorse.
• D8E or F70E (Green) — finish.
• D3F or D3C — field stone / touch-up.

Three stones that cover 95 % of all sharpening in joinery and knife work.

Diamond stone vs ceramic stone vs oil stone

The diamond stone wins on: speed, flatness, coarseness, flexibility (wet/dry), service life.

Ceramic wins on: very fine finish at a low price.

Oil stone wins on: tradition, aesthetics and the super-soft feel on straight razors — but is too slow for modern joinery demands.

For Swedish joiners and knife enthusiasts in 2026, the diamond sharpening stone is the practical default choice. DMT's Diasharp range gives you American quality, a consistent colour-code system and tools that last an entire joinery career.

Starter kits for the workshop

Minimal (chisel + one kitchen knife):

• 1 × D8F (Red / Fine 600)
• 1 × D3F (Red / Fine — field)

Recommended for the serious hobbyist:

• 1 × D8C or D8F (Blue or Red — workbench)
• 1 × D8E or F70E (Green — finish)
• 1 × D3F (field)

The professional workshop:

• 1 × D8X/Black (reprofiling)
• 1 × D8C/Blue
• 1 × D8F/Red
• 1 × D8E/Green
• 1 × D8EE (light green — straight-razor level)
• 1 × A4 set (for the sharpening jig)

Related

• Sanding sponges and sanding plates — the complete guide to hand sanding — for surface sanding of wood before finishing
• See the full knife and sharpening range

Sources

Last updated 2026-04-18.

1. DMT — Official site / FAQ. Manufacturer information on the Diasharp range, colour-code system and manufacturing history since 1976. dmtsharp.com/pages/dmt-faq
2. Sharpening Supplies — DMT Diamond and Ceramic Color Coded Grit Chart. Full table of DMT's colour codes against mesh and micron. sharpeningsupplies.com/blogs/articles/dmt-diamond-and-ceramic-color-coded-grit-chart
3. Axminster Tools — Sharpening with DMT. Industry guide with technique recommendations. axminstertools.com/media/downloads/DMTSharp_mag_article.pdf
4. DMT Sharp — Bench Stones product page. Wet/dry use, cleaning. dmtsharp.com/products/8-in-dia-sharp-bench-stone-extra-extra-fine
5. Cutlery Shoppe — DMT D8EE product spec. Technical data 3 micron / 8000 mesh. cutleryshoppe.com/dmt-d8ee-8-0-dia-sharp-bench-stone-extra-extra-fine-diamond-3-micron-8000-mesh