What Is a Diamond Sharpening Stone? (Grit Chart)
A diamond sharpening stone is a flat plate with diamond abrasive fixed to a steel or composite surface. It can sharpen most steel knives, including hard, wear-resistant steels. Choose the grit by the job: coarse for damage or major reshaping, medium for routine sharpening, and fine for a smoother finish. Grit labels vary, so follow the maker’s guidance.
Buying a diamond plate is an investment in a durable, low-maintenance sharpening surface. The confusing part is often not the price but the labels: a “600” diamond plate does not necessarily cut or finish like a 600-grit waterstone. I compare the stated grit, the knife’s condition, and the maker’s instructions rather than relying on one number alone.
Diamond Stone Construction, Grit Labels & Selection
A diamond sharpening stone holds diamond particles on a flat plate, often made of steel or a composite material. The abrasive may be attached by nickel plating or held in a bonded matrix. Construction affects how the plate wears and how it should be cleaned, so check the product instructions before use.
In common electroplated plates, a thin layer of nickel holds diamond particles on the surface. Other designs suspend diamond abrasive in a bonded matrix. Neither construction makes every plate identical: particle size, distribution, bond, and backing all affect how it cuts. A plate’s label alone cannot tell the whole story.
Diamond abrasive is very hard and can work on most knife steels, including many hard, wear-resistant alloys. That does not mean every knife or edge needs the coarsest plate. A coarse abrasive removes metal quickly, which helps with chips and reshaping but can also remove more steel than needed.
Diamond sharpening stone grit chart
The ranges below are practical guides, not a universal conversion system. Manufacturers may use different grit standards, and diamond grit numbers do not directly match the same numbers on waterstones or sandpaper.
| Labeled diamond grit | Typical task | What to expect |
|---|---|---|
| 140–220 | Repair or substantial reprofiling | Fast metal removal; leaves a coarse scratch pattern |
| 300–400 | Coarse sharpening | Restores a dull edge or continues reshaping |
| 600–800 | General-purpose sharpening | Useful working edge for many kitchen and utility knives |
| 1,000–1,200 | Finer edge and scratch refinement | Smoother finish than a coarse plate |
| 2,000+ | Further refinement or polishing | Finer finish; not required for every knife |
These ranges describe common uses, not guaranteed results. For example, DMT labels its plates 325 (coarse), 600 (fine), and 1,200 (extra fine). Those are DMT’s labels, not exact equivalents to waterstone grit numbers. If a product lists microns or mesh, compare that information only within the stated standard or maker’s system. Abrasive size distributions differ, so a precise cross-brand conversion can mislead.
Key takeaway: Choose the plate for the work, then use its maker’s grit description and instructions. Don’t buy by number alone.
Setup, Sharpening Technique & Grit Progression
Good sharpening starts with a stable plate, a clean surface, and a steady bevel angle. Use the lubricant permitted by the maker, then apply light, controlled strokes. A coarse-to-fine sequence can improve the finish, but you do not need to use every grit for every edge.
Prepare and establish the bevel
- Set the plate on a firm, nonslip surface so it cannot slide during a stroke. Confirm that the abrasive face is clean.
- Read the instructions for lubrication. Some plates are used dry; others allow or recommend water. Oil is not suitable for every diamond plate.
- Hold the knife at a consistent angle that suits its existing bevel or the edge you intend to create. If the angle changes from stroke to stroke, the edge may take longer to sharpen.
- Use controlled strokes with light pressure. Work both sides as appropriate, and check the edge as you go.
A coarse plate is for repair or substantial reprofiling, not simply because a knife feels dull. For a routine touch-up, a medium or finer plate may be enough. Excess pressure is especially risky on a thin or acute edge: it can leave a rough, damaged apex and may speed wear or diamond loss on some plated surfaces. Let the abrasive do the work.
How many grits should you use?
Progress from coarse to fine when you need to remove damage and then reduce the coarse scratches. For a knife with a sound edge that only needs routine sharpening, you can often start at a medium grit and stop when the edge suits its task. Each extra step takes time and does not automatically make the knife perform better.
A useful check is the scratch pattern. If you move to a finer plate, use it until the earlier coarse marks are reduced, then lighten pressure. If the edge is still blunt or damaged, a fine plate alone may take too long to restore it.
Key takeaway: Match the starting grit to the amount of metal you need to remove, not to a fixed sharpening ritual.
Deburring, Cleaning & Stone Care
A burr is a thin lip of metal pushed to one side of the edge during sharpening. Removing it is essential: a remaining burr can make an edge seem sharp briefly, then fold or break away. After sharpening, clean the plate as its maker directs and protect its abrasive face in storage.
Refine and remove the burr
After the bevel is formed, use a finer plate if you want a more refined finish. Reduce pressure as you progress. To deburr, make light, alternating passes from side to side. The goal is to remove the thin lip without rounding the edge.
Check the edge carefully rather than assuming that a higher grit has removed the burr. If the knife still catches or feels inconsistent during a careful test, return to light alternating strokes. Avoid dragging a finger along the edge.
Clean and store the plate
Metal particles left by sharpening are called swarf. Wipe or rinse the plate as the instructions allow, remove the swarf, and dry it if required. Store it so other tools cannot scrape or damage the abrasive face.
Diamond plates do not normally need preheating, seasoning, or flattening. Do not use flattening compounds, oil, or other treatments unless the manufacturer permits them. Different plate designs have different care needs, so the product instructions take priority over general advice.
Key takeaway: Light finishing strokes and clean storage help you get consistent results without adding unnecessary treatments.
Choosing the Finished Edge for the Knife’s Use
The best finish depends on what the knife cuts, not on how high a grit number you can reach. A practical edge for everyday cutting may need less refinement than an edge intended for precise slicing. Start with the task, then choose a suitable grit and stop when the edge works well.
A finer finish can feel smoother, but “finer” is not the same as “better” for every job. A coarse edge can still be useful, while a highly refined edge may be unnecessary for routine kitchen prep. The knife steel, bevel, sharpening technique, and intended use all affect the result.
| Knife condition or task | Sensible starting point | Possible next step |
|---|---|---|
| Visible damage or major bevel change | 140–220 | Move to 300–400, then refine if needed |
| Very dull edge, no major damage | 300–400 | Finish around 600–1,200 as desired |
| Routine sharpening | 600–800 | Stop here or use 1,000–1,200 |
| Edge needs a finer finish | 1,000–1,200 | Consider 2,000+ if useful for the task |
These are starting points, not rules. A knife with a small chip may need local repair before you sharpen the full edge. A knife that is merely losing bite may not need a coarse plate. Use the least aggressive grit that can complete the job at a reasonable pace.
Practical sharpening examples
Consider a kitchen knife with a sound bevel that has become dull. I would begin around 600–800 rather than remove extra steel on a 140-grit plate. If it needs a smoother finish, I could continue to 1,000–1,200, then use light alternating passes to deburr.
For a chipped utility knife that needs substantial repair, a coarse plate may be appropriate. I would work carefully, check progress often, and move to a finer plate once the damage is removed. These examples are task-based guides, not test results for a particular brand or knife.
Key takeaway: The right finished edge is the one suited to the knife’s work, formed without removing more steel than necessary.
Frequently Asked Questions
Are diamond sharpening stones better than waterstones?
Neither is best for every user. Diamond plates are often chosen for low-maintenance use and their ability to sharpen many hard steels. Waterstones have different care and wear characteristics. Compare the specific products and your sharpening needs.
Can a diamond stone sharpen hard knife steel?
Most diamond plates can sharpen a wide range of knife steels, including many hard, wear-resistant alloys. Check the plate maker’s guidance and use light pressure.
Does 600-grit diamond equal 600-grit waterstone?
No. Grit labels rely on different systems and abrasive behavior. Treat the number as a label within that maker’s range, not a universal conversion.
Should I use water or oil on a diamond plate?
Use only the lubricant the manufacturer allows or recommends. Some plates can be used dry; water is permitted for some. Oil is not universally appropriate.
Do diamond sharpening stones need flattening?
They do not normally need flattening like many traditional sharpening stones. Do not apply flattening compounds or treatments unless the maker specifically permits them.
Can I use a coarse diamond plate for every sharpening job?
You can, but it may remove more metal than needed. Reserve very coarse plates for damage, major reshaping, or other tasks that call for fast metal removal.
How do I know when to move to a finer grit?
Move on when the edge has the shape and condition you need from the current plate. A finer plate can refine the scratch pattern, but not every edge needs several stages.
How should I remove the burr?
Use light, alternating strokes on the finishing grit. Check the edge carefully, and avoid pressing hard or dragging a finger along it.
What is the difference between grit and microns?
Grit is a label tied to a rating system; microns describe particle size. They can help compare products only when the standard and particle distribution are clear. There is no exact universal conversion across all makers.
How should I store a diamond plate?
Clean it as directed, dry it if required, and protect its abrasive face from contact with other tools. Follow the maker’s care instructions.
(This article was written by one of our staff writers, Julian R. Hayes. Visit our Meet the Team page.)
