Chips while sharpening Higonokami by Nagao

J

JAWVA

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Aug 17, 2014
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Knife is an authentic Nagao Higonokami, Damascus on blue paper steel.
Out of the box it was somewhat sharp but, had a very toothy feel.
It's a flat grind right to the edge.
I sharpen on a block of scientific granite with various grits of wet dry cloth.
I get my knives scary sharp but this one is confounding me. It seems to chip during the sharpening process. I've never experienced any thing like it. I work from about 600 down to 2000 grit.

I'm wondering if it's a tempering issue.

Anyone have a clue why this might be occurring?

(FYI, I have several high end japanese forge welded lam blades including 3 Murray Carter knives which I sharpen regularly to an edge that cuts before it hits the material.)
 
Pics will have to wait until I'm near my camera with macro. My phone camera isn't going to capture it well.
With a 30x jeweler's loop, the edge resembles the Sawtooth Mountains...jagged and uneven. I can feel it both with my fingers and while cutting with it but, at least with my eyes, it's difficult to easily see.
 
The sandpaper gives a slight cushion so it would be difficult to say your using too much pressure while sharpening. Your issue does sound like too much pressure on a hard stone though.

Have you ruled out thing like technique and sharpening tools?
 
I purchased a knife from a custom maker one time that did this. Turned out to be a bad heat treat, which left the steel very brittle.
 
Jason B. said:
The sandpaper gives a slight cushion so it would be difficult to say your using too much pressure while sharpening. Your issue does sound like too much pressure on a hard stone though.

Have you ruled out thing like technique and sharpening tools?
Click to expand...

I guess I can't completely rule it out but, I've used this system for years, hundreds of times. This is the only knife I have ever experienced this circumstance with. In fact, I'm reluctant to go with another method as I imagine they might be worse.
 
morgaj1 said:
I purchased a knife from a custom maker one time that did this. Turned out to be a bad heat treat, which left the steel very brittle.
Click to expand...

This is the way I'm leaning. it is hard to imagine that Nagao who has been making this knife for better than 40 years would get the heat treat wrong but, the chipping even occurs in the stropping process so, I'm not sure what I have left to think.

I appreciate the replies.
 
Saw into a rock or something coarse + hard + abrasive to flat the edge where you can easily see the dull apex (~0.002-0.005" thick). Now, sharpen it again around 24* inclusive angle. I do this all the time with my newly made knives and zero/almost-zero grind. If the edge is still chippy and or a file still easily bite (instead of skid), yep either bad ht or the edge still has decarburizated steel.
 
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+1 for Bluntcut's comments. And sharpen at a more obtuse angle. Sometimes the heat treat of the edge is too brittle but the steel behind it is OK to excellent. Good luck.

---
Ken
 
So...
I blunted/flattened the edge and used the Ken Onion WorkSharp (first time ever) to reprofile the micro bevel and then hone.
It's now smooth as glass and scary sharp.
I still think the issue was related the original edge temper but, cannot eliminate the sharpening technique I originally used to redress the problem. From a dedicated freehand sharpener to a Ken Oniom Work Sharp fan.... This maybe be the first horse in the coming apocalypse.
 
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