Why did my Japanese knife chip?

Chips usually come from contact with bone, frozen food or hard boards, or from twisting a thin edge sideways. Japanese knives trade some toughness for sharpness, so use a wood or soft-plastic board, cut straight down rather than prying, and keep heavier tasks for a sturdier knife.

Can a chipped knife edge be repaired?

Yes. Small chips grind out on a coarse stone around 400 grit by lowering the edge until the chip is gone, then re-sharpening up through the grits. Deeper chips take longer but are usually fixable on a whetstone, or Knives and Stones can restore the edge for you.

Why Did My Knife Chip or Dull, and How to Fix It

Q: 為什麼我的日本刀會缺角或變鈍，該如何修復？

崩刃來自於硬物碰撞（骨頭、冷凍食品、陶瓷、水槽）；鈍化則源於正常磨耗或不良的刃口。先以粗砥石研磨至崩口處，再重新研磨開鋒。

What causes chips and rapid dulling on Japanese knives, and how to grind out a chip and restore the edge on a whetstone.

觀看

出自 Knives and Stones 工房

我們自家的磨刀與保養教學——點擊即可播放。

Restoring a badly sharpened Japanese knife: the cause and the fix. You probably seen one before

0:00Introduction: a badly sharpened knife

0:31The cause and effect

1:35More problems

2:31Potato test before restoration

3:53How to prevent this from happening?

7:02The restoration: reprofiling and thinning

8:13Refinishing and new edge

10:19Potato test after restoration

0:00The profile that went the wrong way

A new knife curves up at the tip, and this one curved down. You have probably seen the same thing on a friend's knife, or on your own: the middle of the blade is flat, and the tip has hooked over.

A knife, when it's new, should have a curved up, and this knife is curved down.
— from the video

1:47Why it happens

The usual cause is sharpening only the part of the blade you actually use. That section dulls first, so it gets sharpened first, and over time it gets sharpened over and over while the rest of the blade is ignored. The profile goes flat, and then the over-sharpened section starts to hook.

7:20The fix

At this point the knife has lost its chef-knife profile, so the fix is a full reprofile: reshape the blade back to a proper curve, then do a major thinning pass to bring the edge down to the cladding line.

So we are cutting the potato, no longer splitting. And this is the combination of reprofiling, thinning, and sharpening.
— from the video

9:11The moment of truth

The whole job took about forty minutes, most of it thinning. A light refinish on 400 grit cleaned up the scratch pattern, then a fresh edge on 1,000 grit. The result: the potato is cut, not split. That is the combination of reprofiling, thinning, and sharpening.