How to sharpen a ceramic knife with a diamond sharpener

Sharpen a ceramic knife on diamond, and nothing else. Use a diamond wheel sharpener made for ceramic, such as Kyocera's own, or a fine diamond plate (about 1000 to 1200 grit) with very light pressure. Steels, ceramic rods, ordinary pull-throughs and most electric sharpeners won't touch zirconia. Kyocera says home sharpening is fine for chips up to 0.5 mm deep; anything bigger, and any serrated ceramic knife, goes to a service or gets replaced. Our best diamond sharpening stones guide covers the plates in more depth.

Why only diamond works

Most ceramic kitchen knives are zirconium oxide (zirconia). Kyocera's FAQ puts it at 8.2 on the Mohs hardness scale, against 5 to 6 for steel and 10 for diamond. An abrasive has to be harder than the blade to cut it, which rules out a honing steel immediately. Kyocera also says no to ceramic sharpening rods on its knives: those rods are made to sharpen steel. Diamond is the only common abrasive with a clear margin.

The second thing that makes ceramic different is that it's brittle. A steel edge bends and rolls; a zirconia edge chips. That changes two habits. Pressure has to be light, because a heavy hand chips the new edge as fast as it makes it. And you won't feel a burr the way you do on steel, so you check progress by eye and with paper instead.

Chipped or just dull? Decide first

0.5 mm is about the thickness of five sheets of printer paper. Hold the edge under a bright light: a chip you can see as a clear notch from arm's length is usually past it.

What works and what doesn't

The Kyocera RS-20 is the trap here: a Kyocera-branded sharpener that won't sharpen Kyocera's ceramic knives. Check that any sharpener you buy says diamond and names ceramic knives. If a multi-slot electric has one diamond slot and others in carbide or ceramic, only the diamond slot is any use on zirconia.

Method 1: a diamond wheel sharpener

This is the method Kyocera recommends for home use. The Kyocera diamond wheel sharpener has a #1000 diamond wheel and works left- or right-handed. The Kyocera electric diamond sharpener runs on four AA batteries, uses a guide slot and roller to hold the blade, and keeps the grinding dust inside a cover. Both are sold for ceramic and steel knives. Be aware that their Amazon ratings are middling (3.9 and 3.6 stars when we checked), so read recent reviews before you buy.

1. Set the sharpener on a flat counter. On the manual model, hold the body firmly with your other hand.
2. Put the heel of the blade in the slot, edge down, keeping the blade upright and the flat of the knife against the guide.
3. Pull the knife toward you slowly, heel to tip, with no downward pressure beyond the knife's weight. Kyocera's manual roll sharpener has a spring under the wheel that absorbs extra force, which tells you how little force it wants.
4. Repeat several times. On the electric model, let the wheel do the cutting and keep the pull slow and even.
5. Wipe the blade and check the edge under a bright light. A dull spot shows as a thin line of reflected light.

On a chipped edge, keep going until the chip disappears from the edge line, then make a few more light passes. If after a few sessions the chip is still there, it's deeper than a wheel can fix in reasonable time.

Method 2: a diamond plate, freehand

If you already sharpen on stones, a diamond plate gives you more control than a wheel. The SHARPAL 162N (325 and 1200 grit) lists ceramic among the hard materials it sharpens and is used dry. For an occasional ceramic paring knife, the DMT Dia-Sharp credit card set (45, 25 and 9 micron) does the same job in a drawer-size format. Our grit chart converts microns to grit numbers.

1. Color the existing bevel with a marker so you can see you're on it. Kyocera doesn't publish an edge angle that we could find, so match what's there. Our Sharpie trick guide explains how.
2. Start on the fine side (1000 to 1200). Use the coarse 325 side only to grind out a chip, and then only with very light pressure.
3. Make edge-leading strokes with almost no downward force. Think of the weight of the knife plus a fingertip. More pressure chips the edge.
4. Count strokes and alternate sides every few strokes rather than working one side for a long time, since there's no burr to tell you when to switch.
5. Check under a bright light and with the paper test: a sheet held by one corner should slice cleanly from heel to tip.

Expect it to take longer than a steel knife of the same size, because the pressure is so light. If you're deciding between a plate and a water stone for the rest of your knives, whetstone vs diamond stone covers the trade-off, and our DMT lineup guide sorts the cards, Diafolds and bench plates.

Electric sharpeners made for ceramic

Beyond Kyocera's own, the Shenzhen Knives electric diamond sharpener is built for ceramic kitchen knives: 600 grit coarse and 800 grit fine diamond, fixed at 18 degrees per side on coarse and 20 on fine, and its listing says it can grind chips of up to 1 mm. It's a plug-in model, and the listing rules out serrated blades and pocket or hunting knives. The Narcissus S867 uses diamond wheels and its listing names ceramic knives, though it's a general kitchen sharpener rather than a ceramic specialist.

Two cautions with any electric sharpener on ceramic. Feed slowly and never force the knife down into the slot. And treat any claim of handling serrated ceramic with suspicion, since Kyocera itself says not to.

Method 3: mail it to Kyocera's service

For a good knife with real chips, the service is the sensible choice. Kyocera's sharpening page sends owners to its authorized provider, EVERSHARP, in Minneapolis. The service form we checked on October 21, 2026 lists:

• Ceramic knife sharpening: $12 per knife
• Sharpening and blade repair: $17 per knife
• Return shipping: $14 flat
• Turnaround: 5 to 7 business days after it arrives (4 more days if you don't include payment)
• Straight blades only; no serrated knives

The form asks you to roll the knives diagonally in newspaper or heavy paper, box them with enough padding that they can't shift, and leave out sheaths, towels and original packaging. Get a tracking number; EVERSHARP says it isn't liable for lost shipments. The form is linked from Kyocera's sharpening page. For one knife, $26 with return shipping is close to the cost of a home sharpener, so the service makes most sense when you send several at once. Our knife sharpening service cost page compares other services for steel knives.

Avoid the chips in the first place

Most ceramic knives that need sharpening were chipped, not worn. Kyocera's care page lists what to keep them away from:

• Frozen food, bones, pumpkins, coconuts, tough squash and large blocks of hard cheese.
• Prying, twisting, removing avocado pits, opening shells or smashing garlic with the flat of the blade.
• Glass, marble, granite, tile and stone cutting surfaces. Kyocera recommends bamboo, wood or plastic boards.
• Loose storage in a drawer or sink. Use a block, tray or sheath.

Kyocera recommends hand washing. Its FAQ allows the top rack of the dishwasher for plastic-handled models, but says knives last longer washed by hand. Use the ceramic knife for slicing produce, boneless meat and fish, and keep a steel knife for anything that needs force.

Sources: Kyocera International, Resharpening and cutting edge maintenance, FAQ, Care and use guidelines and the EVERSHARP service form, all checked October 21, 2026. Chef'sChoice and AccuSharp limits from the manuals cited in our reviews; Tormek's ceramic claim from our Tormek comparison. Product details and ratings from Amazon listings, October 21, 2026. How we research · Affiliate disclosure