Problem sharpening Aogami Higonokami with Sharpmaker

nozh2002

nozh2002

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Higonokami I bought in Japan out of the box did not shave, so I decide to sharpen them using Sharpmaker. nfortunately Edge start chipping - microscopic pert of the edge falin out! This is only in the middle of the blade - About inch near tip - everything OK and it sharpened to shaving state easy. But other part just impossible to sharpen! I tryed both big and small Higonokamies - result is same. Before I started - edge was straight, but after it starts chopping.

Are there spetial way to sharpent Aogami or Higonokami?
Am I doing it wrong or it is just owerhardened blade?

Also I suspect corrosion involved - I noticed that edge touch brass handle at that area.

Higonokami-08.jpg


Thanks, Vassili.
 
Electrolytic corrosion could be a factor or maybe the edge is just getting banged against the brass. If they are like some of the laminated Japanese knives I've seen, the center is very hard but brittle and would best be honed on a flat stone (they can chip if you steel them or use rod sharpeners because of the very small contact area creating huge stresses and the center of these knives is very hard and brittle... what little force you use to push the knife on a steel or rod sharpener is greatly concentrated into a tiny area)
 
I do not yet own any traditional japanese knives, so my advice here is based on what I have read. (since I am on a shoestring budget, I try to learn as much as I can.)

Japanese knives are indeed very hard and somewhat brittle, and so require special sharpening equipment, namely Japanese waterstones. Waterstones have a _very_ soft bond, and also form an abrasive slurry in use. Both of these features make them supreme at sharpening thin and/or brittle edges.
Get yourself a 1000/4000 or 800/4000 combination waterstone and you will love it! I love mine!
Yuzuha also is correct in his theory and observation.
 
I am waiting for Spyderco benchstones -Med, Fine and UltraFine (ordered already). Do you think It will be OK to use instead of Japanese Stones?

However Part of the blade near tip is OK, I say very OK and I have no such problems with other knives including Shirogamy-Warikomi.

So far I am sharpened it on 30 degrees and continue on 40 with Ultra Fine rods slowly and gentely - so far no luck.

Thanks, Vassili.
 
Maybe.
Waterstones are so soft that the bond between abrasive particles gives way long before the steel can chip. If one is not carefull, you can litterally carve chunks out of it!
 
Vassili, since you have a Sharpmaker, you already have Spyderco benchstones. Turn the base over and lay two rods in the grooves.
 
No, Esav, this is different then just flat horizontal position. It is wide surface which lower pressure on the edge - what important as I understand. I may wait, they are already ordered.

Local Japanese knives are not chisel grinded! This is most important thing I found in Japan (I especially loked for local working knives and bring quite a few of them back), this chisel grind is some kind of modern urban legend. It is only some special kitchen knives like Yanagiba for sushimi etc where it is reasonable (and japanese knifemakers also making European kitchen knives - no problem). But all utility, tools etc - all knives are perfectly normal.

Thanks, Vassili.
 
Spyderco or Moor ceramics should work okay.

I am thinking maybe the middle of the blade is banging the brass when closed, and has maybe cracked parts of the hard steel that are hidden inside the softer steel on the sides so you don't find the cracks until you sharpen away the soft steel to expose the hard center part???
If you have a 10x to 20x loupe or pocket microscope, maybe you could see if there are tiny cracks behind the chips.


Maybe they way you hold the knife when using the sharpmaker could make a difference too... end of blade may be getting less sideways pressure at the end of your sharpening stroke)

Shapton and Norton waterstones would also be good (Norton are less expensive but I hear they wear a bit faster), but most any brand should work.
 
Nothing works so far. Now I am trying to follow your advice - sharpen it with little pressure? almost no pressure at all. Well, it take quite a few time, for sure.

No visible cracks on core, and core layer is thick enough - little bit less then 1mm. I am not sure what it is, my biggest suspition - overhardening, but again I never experience this with other Warikomi I have as well as other japanese knives - all of them are qite impressive. I did not try yet Shirogami Higonokami, so I don't kniw is it because of Aogami or because all Higonokami are like this.

Thanks, Vassili.
 
I had the same experience with Aogami and Shirogami. I don't think they can be sharpened on a Sharpmaker. I think the steels are simply too brittle. I found that very light pressure on the flats of the white rods works ok to maintain a sharp edge, but right now you have to restore the edge on water stones.

www.bladegallery.com offers a sharpening service with waterstones. Maybe you can contact them.
 
Thanks HoB,

I have two other knives with Shirogami and they are just fine.
I sent mail to Kukihide - hope they'll answer.

On you knives - after you sharpened them are there any problem with edge being too brittle during regular use?

So far I think yestarday and this morning I finished sharpen them with Diamond rods with slightest possible pressure, almost without it and it seems work - at least no visible chips. I will try with medium and fine etc. with same gentle touch. We shall see.

Thanks, Vassili.
 
Again similar experience here. The shirogami seemed not quite as fragile as the aogami. But who knows, maybe just a difference in hardness.

On the Aogami knife I have the grays would build with only a few strokes a huge wire edge, which would simply break of, know matter what I would try, and left this really ragged edge with actual chips in the blade that you could see against a light. Sharpening on waterstones was no problem, the edge came back beautifully and it gets INSANELY sharp. Partially because you can really thin out the edge. In regular kitchen use the edge holds up fine. It is not very corrosion resistant and its still pretty brittle, so no banging in the kitchen sink and use of a cutting board (instead of kitchen counter) is a must. But as far as just cutting is concerned, I found the edgeholding very high. The edge essentially never rolls.

Hope that helps?
 
The reason why you need waterstones is the cooling.
Sharpening the sensitive Aogami or Shirogami on a ceramic or God forbid even a diamond rod is a no-no not so much because of brittleness but because of the micro-local heat development destroying the superb hardening of the edge. It's possible to ruin it with that so that it'll never get sharp again.
t.
 
So, It is because of microheating on the edge during sharpening! I used Diamond rods with gentlest possible touch, it seems to work, edge is more straight, then I start with Med with gentlest touch and again I see edge chipping away! Again I use no pressure at all and move slowly. May be it is surface itself overheat it locally. I went back to Diamond rods and will try to skip Med this time and continue with Fine and UltraFine.

Thanks, Vassili.
 
From an abrasive manufacturer's site "Diamond is not useful in grinding steel or ferrous alloys because carbon or diamond readily dissolves or reacts with iron." This happens even with a coolant because of micro heating. So they recommend cubic boron nitride for iron and steel. They were talking about power grinding and cutting. This would also be true with hand grinding, but to a much lower degree so it is usually not a problem with hand sharpening on diamond rods.

But, if you want to experiment, you could try using some oil or water (I find ammonia-based window cleaner works well... it is mostly water with a little soap for lubrication and the ammonia raises the pH and helps prevent rust... iron rusts when the pH drops below about 8 and plain water is usually around 7 or lower). Can't hurt... might help!

You can use water on your Spyderco stones when they arrive too, but don't use oil or you'll never get it back out of the stones.
 
...Alittle off-topic, but if those knives that you are trying to sharpen are so brittle as to chip by just sharpening 'em, I'd toss 'em out and buy a couple Benchmades...I could sharpen my Benchmades on a brick, and they wouldn't chip!
 
glockman99 said:
...Alittle off-topic, but if those knives that you are trying to sharpen are so brittle as to chip by just sharpening 'em, I'd toss 'em out and buy a couple Benchmades...I could sharpen my Benchmades on a brick, and they wouldn't chip!
Click to expand...
I am keeping in mind this thought also, however I may expect from Japanese knives superior quality then from Benchmade etc, with Aogamy YSS, laminated blades etc. This is why I try to fully understand what is going on. Is it overhardened or it is me sharpening it wrong way, they have different knive culture which may require different approaches.

And the way you answering - anybody can answer to you. Something like - "Why did you spend $100 or more for Benchmade if you can buy boxcutter to do same and don't sharpen it at all, so I'd toss Benchmade out and buy a couple Boxcutters". (It is not my opinion, I just demonstrate you were I think you are wrong, I just mechanically change words in your statement. Personaly I am big fan of BM).

Are you certan that it is HT failure to suggesting this? If so - speak out. If you are not - don't give this kind of advices to me.

I am not yet convinced until I see that nothing helps.

Thanks, Vassili.
 
glockman99 said:
...Alittle off-topic, but if those knives that you are trying to sharpen are so brittle as to chip by just sharpening 'em, I'd toss 'em out and buy a couple Benchmades...I could sharpen my Benchmades on a brick, and they wouldn't chip!
Click to expand...

Oh, I wouldn't go that far. Granted, these are pretty inexpensive knives so they were probably machine ground, and the steel is a bit finicky in the first place, but it is worth a shot.

I had a SOG x42 autoclip in BG-42 that had the same problem. The edge chipped, and even chipped while sharpening on water stones, but they'd just overheated and ruined the steel on the edge when they ground it on the machines. I just slopped some daimond coolant on my medium DMT plate and kept at it until I'd ground the edge back a mm or two and finally got past the bad part. Now it has a really great tough edge... even rebeveled down to 10 degrees per side. I would have thought BG-42 was crap steel if I hadn't spent a couple of hours grinding off the heat-damaged edge (and rounding the corner on that fake tanto point... I like the American tanto shape but hate that sharp corner so I regrind them to a steep curve). Now it is my favorite household utility knife, though I wonder about SOG's quality control (I'll cut them some slack since it is a nice knife and I was going to mutate it anyway).

Nozh2002 may have the same problem with these if they were initially shaped on a grinding wheel. Japanese laminated blades and rod sharpeners don't get on well because of the brittle core (as HoB can attest), but these sound exceptionally brittle. When he gets the stones he ordered, he can slop some water on the medium stone (probably should have gotten a coarse stone or 600 grit diamond lapping plate too) and grind the edges back a ways and see if there is tougher steel behind the edge.
 
Well, gentle touch does not work - still does not shave, so I will try to take away as much "bad" steel from the edge as possible.

Only question I have - if it is overheated by grinding, it suppose to be soft, not brittle?

Thanks, Vassili.
 
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