Shun Chips

[Ziggy]

I know I’ve been blathering about chips in Shuns and my theory that it is bubbles in the VG-10 or interior metal itself.

Finally took a pic, crappy but you get the idea.
Edge was all chipped, stripped it down and in process of rebuilding the edge.
Low and behold, as metal gets taken off, these holes start to show up and enlarge.

Here is a shot of 1, there are several on this chef’s knife.
Its my belief that as the edge wears, the holes in the metal are exposed and then form a chip.
Any thoughts?

Attachments:

• shun_hole.jpg

[Ziggy]

Sorry, it landed in welcome mat by accident.
Any way someone can move to Sharpening as a Business or a more relevant info category?

[Josh]

So are we looking at the dark spot in the edge? is it actually detented in like a hollowed out bubble would be?

[Ziggy]

So are we looking at the dark spot in the edge? is it actually detented in like a hollowed out bubble would be?

Yepper Josh. You can poke a pin in it and wobble it.
They are the beginnings of a larger hole, than smaller if you grind through.
They appear as chips on the edge, but I think are actually air pockets exposed through wear at the apex.
Once opened, they turn into chips.

This problem has been 90% consistent with the VG-10 as well as the Kai series for me.
If not for close inspection, it just feels like a tiny bump on a paperpush, or a snag.

[Josh]

yeah that’s really weird ziggy… i have never experienced that myself and I have tested several blades. I will try to get some pics w/ my usb scope on the next few I do. What magnification level is that?

[Ziggy]

No Clue, just used my small pocket panasonic I use for fishing and zoomed in all the way and held a flashlight to it 🙂

I was in the middle of knocking out the batch and wanted a quick shot, get them done, bagged and tagged.
Didn’t want to break out the SLR Macro gear and flash.

It is really small to catch while sharpening … glasses and good lighting gives them away.
I’d say about 6 are on the one side alone.

I’ve seen the same on Globals, not much you can do, I don’t want to eat all that VG-10 to get to it, it’ll only expose more.

Next time you get a set, slide the edge of a razor over the edge, you’ll feel them right away, than see them is your eyes are good.

I just rip the edge off once spotted and reprofile.
If I can get to 1K without a chip on the edge I’m happy, customer is happy 🙂
Than give it a polish.

[Cliff Stamp]

First, I would like to congratulate you on the experimentation, few people go that far, most would have just wrote off the steel and/or brand, nice detective work.

I have seen that commonly on heavily used knives, especially knives used in salt water as it is pitting damage and can be present even when it isn’t visible – but there are usually signs of it on the main blade.

What you have isn’t like corrosion as you would have seen evidence of it on the blade I would imagine. There are things which can cause the same problems in steel, non metallic inclusions for example.

How often do you see it on the Shun blades?

[Ziggy]

Chips are there 90% of the time, especially the Kai line.
I knew there were chips, this and other holes were exposed during reprofile.
They start out in the wall small, then larger, then smaller as you take away more metal, so am thinking air pocket of sorts.

That new steel so you’re not looking at pitting.

Funny thing too, this batch was fatigued at the edge.
I flattened till I hit rockhard, then started the reprofile.
Bur was flaking off … in actual flakes until I hit hard steel.

Someone also had a grinder to these before, not super bad, and even grind, but too high up the sidewall. Line was pretty well set, so I’m not thinking freehand on a wheel.
More like 2 wheels making a hollow grind set in depth.
I always see a correlation to those types of grind and fatigue.

Oh, this was at maybe 200 grit, before next steps.

[Cliff Stamp]

If there was a power grinder used then there are many things which could be causing the problem related to very high heat and possible non-stainless contamination. It could be nothing more than burnishing/welding of non-stainless steel which then rusts out.

Have you seen it on knives which were not power sharpened?

[Ziggy]

yepper,
even seen it if I was the first one to sharpen them.
goin back now about 3 years I’ve been catching these.

the grinders i think kill the steel and cause the fatigue I think but not the internal air pockets, just my guess.
Very much like when you get a beat up serrated knife and the scallops never stop dropping burs until you’re well into them, same feeling.

Caphalon makes a line identical to the Kai, guessing same manufacturer (Kershaw?), just a retread.
Same exact problems with pockets.

[Josh]

I would be interested in checking with Clay to see if you could send it to him and he could get some pics at 800x or 1600x and maybe that would clue us in more…

[Ziggy]

Would love to Josh but customer knives, bagged and tagged ready for drop in morning.

[Josh]

ahhhh that’s right! I forgot about that… that stinks!

[Josh]

Ok… so yesterday I was sharpening some KitchenAid knives on my belt sander.

I noticed that the edge kept chipping out on a few of them, no matter how much I “destressed” the edge! So finally I just finished them… but when I was looking with the naked eye I could see little inclusions in the edge, so I snapped a few photos.

This is what they look like further down the bevel:

And this is what they look like at the very edge:

Very strange indeed… it’s like they didn’t use clean steel when starting??

[Ziggy]

I wouldn’t be surprised.
I find the Kitchen Edge metals hit or miss, pretty low on the food chain and quick to find for $8.00 at Home Goods.

The Santoku metal is particularly bad and too thin.

[Author]

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