PDA

View Full Version : How do you decide that you've reached the ultimate sharpness a particular blade can attain?



tk59
05-11-2011, 05:27 PM
Back in the old Kitchen several month ago, Jon essentially posted a survey of who thought what steels would achieve the sharpest edge. There and elsewhere, I continue to see people post about how certain steels just get way sharper than others and I'd like to ask a couple of follow-up questions:

1. Do you all sharpen different steels differently? ie different stones, different amount of time on each stone, etc.
2. How hard did you try to achieve whatever you consider to be an "ultimate" edge?

The reason I ask is I spend a LOT of time working to achieve "ultimate" edges with all of the knives I ever lay hands on and it's been months since I failed to achieve that sort of edge with any steel regardless of hardness, comp, maker, ht, etc. The big difference I find is pretty much how much time it takes to get there and how long it lasts and that's pretty much it.

EdipisReks
05-11-2011, 05:48 PM
i've never attained what i think the steel can hypothetically do. a precise and powerful laser and an electron microscope would probably be necessary for that (i have access to the microscope, but not to the laser). i sharpen until the knife will push cut tomatoes and shave arm hair just by touching the edge to the hair. i find that a knife that can do those two things will stay pleasingly sharp through any amount of cutting i'm likely to do at home. i find this level of sharpness to be pretty easy to attain, not taking more than 10 or 15 minutes, starting from a knife that has an adequate bevel angle.

i find going sharper than that level (the sharpness needed for the weight test that Salty showed off your edge with, for instance, which i got with my newest knife that i was re-sharpening from scratch anyway, so figured i might as well, but which i doubt i'll try to achieve with my others that stay at my preferred sharpness level) to take a lot of time and effort with the tools i have at hand (i polish with a kitayama and then strop for a minute or two on .5 CrO and then .25 diamond) and that level of sharpness isn't noticeably different from the normal level i'll accept when actually cutting food. i've become jaded, and i don't think i'll ever obtain that feeling of extreme sharpness that i felt the first time i used a Shun with the OOTB edge, after years of poorly sharpened (by me) German knives. i came to the same conclusion about hops, and i've quit chasing that initial bitterness i experienced upon my first good IPA. first loves are the most intense, in many ways, and can't easily be recaptured, so i've quit chasing them, even thought i know that what i accept as good enough really isn't, in all ways.

tk59
05-11-2011, 05:57 PM
That's fair. I don't sharpen like that often either but I feel the need to do it once on each blade I get my hands on. I know what you mean by the "feeling" you described trying out your first really sharp edge. It's been a while since I thought about it.

rockbox
05-11-2011, 05:58 PM
How do I decide that I reached the ultimate sharpness a particular blade can attain? When I can convince someone like you or Mario to sharpen my knife.

tk59
05-11-2011, 06:05 PM
:happy2: I'd sharpen your knives anyday, Rock. I go around asking people for knives to sharpen all the time. I did that to a local sushi chef yesterday and he looked at me like I was ***** crazy. BTW, I know what you mean about Mario. That Heiji Mario sent was hair-whittling sharp and it wasn't even a fresh edge.

EdipisReks
05-11-2011, 06:08 PM
Yeah, the Shigi he sent me was damned sharp, too. I didn't really need to put my own edge on it, I just like using my own work.

tk59
05-11-2011, 06:10 PM
...I just like using my own work. Me, too. I made dinner with it and then sharpened it...

stevenStefano
05-11-2011, 06:15 PM
I think the first time you use or sharpen a good knife, it seems to be much sharper than any other time, even though it isn't. I think I'm going to spend a lot more time in the mid-range grits of my knives, I spend a lot less time there than I do at the coarser stages, and I want to see if it makes much difference to the edges

EdipisReks
05-11-2011, 07:13 PM
Me, too. I made dinner with it and then sharpened it...

that's what i did, too. :)

Cadillac J
05-11-2011, 09:13 PM
TK, I feel like we have the exact same outlook and passion for sharpening(although I don't take anything past a 10K SS). After two years and hundreds of knives sharpened, I still get excited to do so each and every time.

I've never agreed with comments like "white gets much sharper than blue", etc. Each knife is different and I think it is hard to talk in general terms like that, as I'm sure my Takeda could make someone re-think that white#2 can get 'the sharpest'. My aogami super, white#2, 19c27, semi-stainless knives all have amazing edges on them, and although different from one another, I consider them to be a similar league as far as performance is concerned.

Not sure if I reached the ultimate edge, but I know that I'm really happy with the edges I produce...they make cutting/cooking so much fun.

Tristan
05-11-2011, 11:47 PM
I'm so very far from that... I only take my edges up to 5K being a novice. Was really stoked when my carbonext came off the 5k with an edge that scared me a little! But after just a week of home use, it seems so dull.

Must have just left a weak wire edge on the side that Dave keeps mentioning. Sigh. Was feeling quite ****** when I realised how crap I was compared to you guys. Back to the stones again this weekend.

JohnnyChance
05-12-2011, 02:10 AM
I have only been sharpening seriously for a couple of years and haven't been passionate about it the majority of that time. When working a lot it was more of a chore than a fun or relaxing exercise. And only recently have I been getting more and more equipment (stones, strops, compounds, etc). So for me, every time I sharpen a knife (that I take my time on, not just a quick touch up before work) it is the best edge I have put on a knife. I am still learning, and get a little better each time, raising the bar, even if only slightly.

Tinh, are you a regular at the sushi bar? Maybe to gain his trust you could bring in one of your knives for him to try so he knows you aren't taking it to a Chef's Choice. Also, are you equally skilled with single bevel sharpening?

tk59
05-12-2011, 02:12 AM
I'm so very far from that... I only take my edges up to 5K being a novice.
You don't need anything more than a 5k. I used a couple of high grit stones mainly because I had some cool knives for a one shot deal and I wanted to try some different stones that wouldn't grind a lot of Salty's precious metal off. The other reason is high grit stones will remove your burr/wire edge if you are careful.


Must have just left a weak wire edge on the side that Dave keeps mentioning. Sigh. Was feeling quite ****** when I realised how crap I was compared to you guys. Back to the stones again this weekend.
Easiest way to rapidly improve your edge is to finish with a handful of VERY light strokes on both sides of your edge and get a cheap leather strop, load it with chromium oxide or diamond and abrade that wire edge off. Finish with light strokes and listen to the sound. It shouldn't sound like it's slipping across the leather. You should hear a very faint scraping. If you pick up your knife and there's a bunch of leather "dust" on your blade, the scraping isn't faint enough. If you don't want to get a leather strop, almost anything will work but it will take longer. If it still doesn't work, you can raise your angle some to work off the burr. You'll get a microbevel but at least it'll be a stronger edge...
It seems like yesterday that I was in your exact shoes except I learned to sharpen on a crystolon oil stone (yuck) and then went to a 3kSS single water stone solution. That was tough. Lots of gouging for a while.

mattrud
05-12-2011, 02:19 AM
Regardless of steel most of my knives are very close in their level of sharpness due to the angles not the steel itself, the ease of sharpening and the feel of the edge may be different, the only times I may have a knife be sharper than most of the others are the knives I have very large bevels on (i.e. lower angle of sharpening) but at the same time edge retention can come into question depending on steel. I rarely use large bevels and sharpen at super fine angles. I need edge retention in the kitchen and my mind set is more that the edge is coming to a finite point and not just focusing on how low of an angle i am sharpening at.

tk59
05-12-2011, 02:21 AM
TK, I feel like we have the exact same outlook and passion for sharpening(although I don't take anything past a 10K SS). After two years and hundreds of knives sharpened, I still get excited to do so each and every time.

I've never agreed with comments like "white gets much sharper than blue", etc. Each knife is different and I think it is hard to talk in general terms like that, as I'm sure my Takeda could make someone re-think that white#2 can get 'the sharpest'. My aogami super, white#2, 19c27, semi-stainless knives all have amazing edges on them, and although different from one another, I consider them to be a similar league as far as performance is concerned.

Not sure if I reached the ultimate edge, but I know that I'm really happy with the edges I produce...they make cutting/cooking so much fun.

It's nice to know I'm not alone. I mostly finish on 8k Kit, SS, 12k SS or belgian coticule and then either chromium oxide or diamond loaded strop. The 20k is usually just my shaving stone. I haven't shaved with anything other than a knife in a few months now. I'm looking forward to getting a nice straight razor at some point.

tk59
05-12-2011, 02:44 AM
...Tinh, are you a regular at the sushi bar? Maybe to gain his trust you could bring in one of your knives for him to try so he knows you aren't taking it to a Chef's Choice. Also, are you equally skilled with single bevel sharpening? Okay, what actually happened is I showed up and noticed that he had some chipping issues. So I'm staring at this guy's knife trying to figure out what the problem is while he's using it and he's working behind a glass shield so I must have looked a little suspect. I finally decided he was grinding his convex edge too flat with no micro. I basically told him just that and offered to help him with it. That's when he gave me the "are you crazy" look. After some more sharpening talk, I guess he decided it was okay to let me have a go at it. I have to say I wasn't expecting that response and I've never sharpened a large single bevel knife before so I'm a little uptight about it. Luckily, I have some knowledgable back-up.

Lefty
05-12-2011, 10:56 AM
Okay, what actually happened is I showed up and noticed that he had some chipping issues. So I'm staring at this guy's knife trying to figure out what the problem is while he's using it and he's working behind a glass shield so I must have looked a little suspect. I finally decided he was grinding his convex edge too flat with no micro. I basically told him just that and offered to help him with it. That's when he gave me the "are you crazy" look. After some more sharpening talk, I guess he decided it was okay to let me have a go at it. I have to say I wasn't expecting that response and I've never sharpened a large single bevel knife before so I'm a little uptight about it. Luckily, I have some knowledgable back-up.

My story isn't quite related, but yours really reminded me of last weekend, when I was at a Korean/Japanese restaurant (man, can they make food!).
I was watching the chef for a few minutes and finally I asked him about his knife. His response was "not like your knives. This is made in Japan". I tried to explain my situation and the fact that I actually understand knives, shapes, etc. I finally got out of him "Doi", and "95/5". It didn't look like a Doi, and it sure didn't look 95/5 (on a yanagi??), unless it was a kiritsuke, and he added a back bevel. Either way, he wasn't letting me get anywhere near his knife...I was still to far away to tell. Dang!
I find it funny that more chefs don't trust the knowledge of patrons who are asking specifically about their knives. I realize there are those who go and ask because they "ain't never seen a knife like that", but it would have been nice to get a real look at this guy's kit. His skills are likely the best I've seen around here and I would have loved to do a little shop talk.
Oh well.
At least the food was AMAZING!

Cadillac J
05-12-2011, 11:06 AM
I mostly finish on 8k Kit, SS, 12k SS or belgian coticule and then either chromium oxide or diamond loaded strop.

90% of the time my finishing is just on my 5K SS followed by stropping on felt/diamond and leather/chromium...this is quick and easy, and the 5K finish is really a perfect middle ground for polish and bite.

But I do take my carbon steels up to the 10K once in a while, depending on my mood.

How did the Gesshin compare to the Naniwa SS or other stones you've used?

EdipisReks
05-12-2011, 11:25 AM
Okay, what actually happened is I showed up and noticed that he had some chipping issues. So I'm staring at this guy's knife trying to figure out what the problem is while he's using it and he's working behind a glass shield so I must have looked a little suspect. I finally decided he was grinding his convex edge too flat with no micro. I basically told him just that and offered to help him with it. That's when he gave me the "are you crazy" look. After some more sharpening talk, I guess he decided it was okay to let me have a go at it. I have to say I wasn't expecting that response and I've never sharpened a large single bevel knife before so I'm a little uptight about it. Luckily, I have some knowledgable back-up.

i lent my Yanagi and Usuba to a sushi chef at a restaurant a friend of mine is a hostess at. both knives were very well received, which made me feel really good. i don't speak Japanese, so i'm just going by what my friend, who does, said, but both knives had been pretty obviously used heavily. i've had knife conversations at several restaurants, both Western and Asian. at New Years Eve, last year, our waiter even went back and brought out one of the knives used in the kitchen, after service was finished. this was at a really good French restaurant. it was a Misono 210 Molybdenum gyuto. i hadn't gone out of my way to get into a knife conversation, he was just very attentive and overheard me wondering aloud at my girlfriend about their cutlery. after he and i started talking about knives, i noticed the we got more service than the tables immediately around us. ;)

anyway, i've been finishing on the Kitayama and then .5 CrO and then .25 diamond (both on balsa) for a few months, now. i had stopped at 6k for a couple years before that, and i had been happy with the 6k finish. it was only when i wondered how much sharper i could get my edges that i bought my first strop, and then bought the Kitayama (and then another strop, and then started making me own strops). i've come to the conclusion that 90% of the keenness of a given edge is determined by how even of a scratch pattern is put down by the medium stones used. you can create a nice sharp knife even when the coarse bevel is sloppy, by fixing it with the medium stones, but it's really hard to fix a knife with finishing stones when the medium stage has been done poorly. i'm planning on getting a Takashima from Jon soon (hopefully next month), but it's more because i want to start trying natural stones than it is because i'm unhappy with the performance i'm getting off the Kitayama.

Lefty
05-12-2011, 11:33 AM
Great knife, that chef was using! :)

EdipisReks
05-12-2011, 11:36 AM
Great knife, that chef was using! :)

yeah, i figured you'd like that. :)

Lefty
05-12-2011, 11:50 AM
Haha. Stupid price increase....

tk59
05-12-2011, 02:05 PM
90% of the time my finishing is just on my 5K SS followed by stropping on felt/diamond and leather/chromium...this is quick and easy, and the 5K finish is really a perfect middle ground for polish and bite.

But I do take my carbon steels up to the 10K once in a while, depending on my mood.

How did the Gesshin compare to the Naniwa SS or other stones you've used?

I always keep a couple of 5k edges around in case I want a more aggressive cutter.

As for the stones, I would say the Gesshin 1k is a best in class stone. It's just like a Beston 1.2k but it's spash n go so it dries and I put it away in a few hours rather than days or having to have a permasoak bucket. I need all my storage space for other knife junk and a bucket just doesn't fit nicely into my equation. The finish is similar but probably a bit finer-looking. I think it feels a little harder but again, that's similar and so is the level of feedback. It is also similar in terms of speed. It is my go-to 1k stone.
Gesshin 5k is also splash n go. It is a really nice stone. I like everthing about it except it's a bit slow. If I'm using it to refine a 1k edge, it's great. If I really want to grind out all the 1k scratches, it takes a bit longer so I've started inserting a 3kSS into the progression. The 20k is superfine and damn hard and probably isn't the best stone for kitchen knives, as much as I hate admitting it. There's just very little bite to that edge and since it's so hard, it's a bit difficult to get it to touch every point along the edge unless you purposefully go for a tiny microbevel.

StephanFowler
05-12-2011, 04:06 PM
i've come to the conclusion that 90% of the keenness of a given edge is determined by how even of a scratch pattern is put down by the medium stones used. you can create a nice sharp knife even when the coarse bevel is sloppy, by fixing it with the medium stones, but it's really hard to fix a knife with finishing stones when the medium stage has been done poorly. i'm planning on getting a Takashima from Jon soon (hopefully next month), but it's more because i want to start trying natural stones than it is because i'm unhappy with the performance i'm getting off the Kitayama.


similarly, I have found over the years that the more time I take getting everything just right at 36grit on the grinder, the easier I can clean it up with 80 grit,
when I'm hand sanding I start at 150grit and work up to 2000, If I take my time at 150 and get everything just right I can get from 150 to 2000 in a matter of 20-30 minutes. If I try and rush the 150 finish it can take significantly longer to get to 2000.

Eamon Burke
05-12-2011, 05:21 PM
I've learned a lot about sharpening by learning to sharpen different things--cheap steel, high end steel, straight razors, scissors, etc.

It is my firm belief that a tool is properly sharp when you never give a second thought to it. When your tool becomes a part of your day, it is not doing it's job. A tool's job is to disappear into your workspace, and let you focus on the task at hand, whether it is cooking dinner, cutting hair, shaving, opening boxes, or skinning a deer.

Sadly, lately, I've had to re-consider my stance on my three knife rule. I no longer think 1 knife is perfect for 90% of tasks. It's more like 45%, because different food items require different kinds of sharp. I found this out when I sharpened a guy's knife to a hair popping edge, and it just fell through carrots---and smashed a tomato. Then I roughed it up on a 1k stone, and it fell through a tomato, but sawed it's way through the carrot. You need polish for fish, teeth for chicken, etc etc.

Surprise, surprise the Japanese had it right about knives again.

*edit* and on medium stone quality, I learned a lot from straight razor guys that sharpen on 2 stones, and 2 stones only, but they don't go from 1k to 6k until the 1k will shave without effort.

EdipisReks
05-12-2011, 05:39 PM
i find that to be strange, the idea that a knife that will slide through a tomato won't slide through a carrot. the knives i have that will push cut tomatoes don't even know the carrots are there.

NO ChoP!
05-12-2011, 05:45 PM
Maybe the carrot to tomato isn't as good a reference as say, a crispy, charred, grilled tenderloin to a tomato...

EdipisReks
05-12-2011, 05:49 PM
i cut crispy, charred, grilled tenderloins with no problems using the same knives. i agree that toothy edges can feel different than slick edges, but i don't find either to really cut much different if they are both prepared similarly. i may have a different definition of toothy, though. white steel, for instance, always feels toothy to me, no matter how much time i put in to making the scratch pattern as uniform and polished as possible.

Eamon Burke
05-12-2011, 07:26 PM
Maybe the carrot to tomato isn't as good a reference as say, a crispy, charred, grilled tenderloin to a tomato...

Well, it wasn't a reference. It really happened. Dumbfounded me for sure. Just like the time I had a knife that would shave my armhair, and wouldn't break the peel of a potato.

The thing is, a crispy, grilled tenderloin needs the same toothy edge as a tomato. Unless your tomatoes are bulletproof, straight-outta-the-warehouse, they will benefit from an edge with some bite to it. God knows I cut enough tomatoes at work.

But a carrot needs a polished, push-cutting edge, much like you would want for wood carving.

Eamon Burke
05-12-2011, 07:28 PM
i cut crispy, charred, grilled tenderloins with no problems using the same knives. i agree that toothy edges can feel different than slick edges, but i don't find either to really cut much different if they are both prepared similarly. i may have a different definition of toothy, though. white steel, for instance, always feels toothy to me, no matter how much time i put in to making the scratch pattern as uniform and polished as possible.

What kind of cutlery are you using? Variety is the key here. Comparing a Shigefusa to a Tojiro is really not that great of a leap. Comparing a Takeda to a Chicago Cutlery, however, you will find that different knife designs and steels will require different edges to perform similar tasks.

EdipisReks
05-12-2011, 07:31 PM
the same edge that allows me to easily cut translucent slices of carrots needs a quarter inch of forward movement to cut through the ripest and juiciest heirloom tomatoes grown 15 miles away from where i live. *shrug*

EdipisReks
05-12-2011, 07:32 PM
What kind of cutlery are you using? Variety is the key here. Comparing a Shigefusa to a Tojiro is really not that great of a leap. Comparing a Takeda to a Chicago Cutlery, however, you will find that different knife designs and steels will require different edges to perform similar tasks.

my current gyutos are Mizuno Blue, Hattori FH, Konosuke White, and Shigefusa. i've owned Akifusa, Shun, Tohiro, and Yoshihiro gyutos and chefs knives. i've had the same experience with all of them. my Usuba cuts everything the same way with the same polished edge i put on my gyutos. i haven't used a cheap knife in a long time.

Eamon Burke
05-12-2011, 07:40 PM
That is the reason why you do so well with polished edges! I don't deal with as much high-quality steel personally as this forum discusses it, and the edge in question was on a 20 year old Chicago Cutlery Walnut Tradition Chef's knife. I've heard that cheap knives do best with cheap sharpening, but I never understood it until then.

EdipisReks
05-12-2011, 07:47 PM
hmm. i could see that. i can also see why a blade that can shave a hair can't cut a tomato. the blade in your Schick isn't all that sharp, after all.

Lefty
05-12-2011, 07:51 PM
I'd bet my life savings on my knives not being even close to their "full potential" in the sharpness department. They are however, VERY sharp (I've burst my knuckles and tips like overripe cherry tomatoes by accidentally tapping the edge).
The funny thing is, I don't want them as sharp as humanly possible. I like my edges to be able to shave with 1k, then I refine it on a couple finer grits. My bevel angle is about 12-15, per side, depending on the knife.
Even though I'm an admitted sharp addict, I like a bit more stability in my edges than a lot of guys here. To me, I like an edge that I can use - beat up on - and the next time I need the same knife, a quick stropping is more than enough. To be honest, I feel my edges aren't a true success if they don't last for AT LEAST a week.
Let's not forget, these are tools that we hope to have around for a long time. If we thin a knife and keep it going at sub 10* angles and sharpen every two or three days, how long will we be able to use the knives we love so much?
There's a balance and I hope to achieve it every time I sharpen.

EdipisReks
05-12-2011, 07:56 PM
you can always buy a new one if you wear it out.

Lefty
05-12-2011, 07:58 PM
Have you no heart? Haha

EdipisReks
05-12-2011, 07:59 PM
nope, i cut it out by accidentally tapping my knife edge against my chest.

Lefty
05-12-2011, 08:03 PM
That sounds about right! :p

Tristan
05-13-2011, 12:08 AM
Easiest way to rapidly improve your edge is to finish with a handful of VERY light strokes on both sides of your edge and get a cheap leather strop, load it with chromium oxide or diamond and abrade that wire edge off. Finish with light strokes and listen to the sound. It shouldn't sound like it's slipping across the leather. You should hear a very faint scraping. If you pick up your knife and there's a bunch of leather "dust" on your blade, the scraping isn't faint enough. If you don't want to get a leather strop, almost anything will work but it will take longer. If it still doesn't work, you can raise your angle some to work off the burr. You'll get a microbevel but at least it'll be a stronger edge...
It seems like yesterday that I was in your exact shoes except I learned to sharpen on a crystolon oil stone (yuck) and then went to a 3kSS single water stone solution. That was tough. Lots of gouging for a while.

I purcased a leather pad, and what looks like a crayon of chromium oxide. It comes in a hard cardboard tube, and the chromium itself it not a paste - it is like a very very hard crayon. Do i just rub it on the pad? Or does the chromium need to be prepped in some way?

tk59
05-13-2011, 12:16 AM
There's no prep necessary. You can just rub the crayon on the leather until it's all green (hopefully, it isn't as hard as you're making it sound) then go to town. Go slow and make sure you check out what's going on and check out your edge after a few strokes. Get to know your equipment.

Tristan
05-13-2011, 02:52 AM
Ok, I typically use full strokes the way curtis does it in his videos... I realise it isn't like the de facto way here on the forum...

I've alternated learning full strokes and also doing sectioning... I scuffed a blade pretty badly through sectioning and realised I wasn't keeping the angle consistent, somehow a full stroke seems easier to me.

rockbox
05-13-2011, 10:30 AM
Tinh,

Here is a million dollar question. Can you pass your tomato test with a forschner? I understand that the edge may not last at all but can it pass it one time?

Cadillac J
05-13-2011, 11:07 AM
My passion for rubbing steel to rocks will never go away, but I no longer feel I'm trying to chase some mythical 'perfect' edge---I know what I like, and I know how to sharpen to meet these requirements. I would estimate all my versatile double-beveled knives are between 8-12 degrees per side, extremely sharp, and they hold up really well with my cutting style in my environment...they might not be for everyone, but seem perfect for me.

Sharpness is all relative as we all know---a Wusthof might of been the sharpest knife you used years ago, but now it might not meet your current standards at all---edges you were happy with on your Tojiro in the first few months of sharpening, might embarrass you today if your results were the same. The whole reason I got into Japanese knives and whetstones in the first place is because I wasn't happy with the performance of European and other knives, so I was searching for something on a whole new level. It seems to be either discontent with the present, or curiosity of what could be, that push us to get to that next level.

mikemac
05-13-2011, 11:48 AM
...Sharpness is all relative ...

So these discussions always seem to make my head spin (and I'm sure Dave will see my post and be somewhere between :bashhead: and :crying: ...sorry Dave)

Throw edge retention out the window for now....

Sharpness - for the sake of the discussion add an EP for consistency. Set the angle to "X" - could be 10, or 12 or... doesn't matter. And limit this to a 1k stone....no more, no less. Raise a burr on one side, flip the blade, push the burr to the other side, de burr with hard felt or cork, back to the EP, repeat to refine the edge, but still with only the 1k, and finally use the EP w/ 1k to strop.

Is a Forschner equally as sharp as a Shige, or Watanabe, Carter, Konosuke at this point? Each knife - exact same angle, stone, etc.
Are they or are they not all equally sharp? Why?

Now do the same with Blue #2, White, AS, CrMo, or PS quenched in virgin dew....aren't they still equally sharp?

OK - now change the scenario...this time what about Polish? If you start with two identical knives, and angles remain constant, but one is sharpened with the 1k, and the other is taken up thru the progression to a 5k or 10k....do you think one is 'sharper' than the other ? Why?

Cadillac J
05-13-2011, 12:08 PM
Mike, not sure if your questions were directed at me or not, but here is my quick overall opinion, although I don't think it really help answer your questions (sorry!)

I'll be honest and say that I'm not even sure what a good definition of sharpness is...we might judge it by how easily the edge cuts things, but other factors such as geometry and whatnot also come into play that might alter our perceptions of one knife being 'sharper' than another. Even if an objective test was created...would it matter? If your favorite knife felt like the sharpest in your arsenal, yet when tested, it was found to be lower on the 'sharpness meter', would it change how you viewed this knife?

All I care about is if my knives cut how I like/expect them to for their intended purpose---if not, they need some work...if so, smiles all around.

Sometimes I think we tend to complicate things in search of 'truths', or based on other peoples' personal experiences reflected upon our own. Nothing wrong with that at all, but I like to keep things simple and do what works for me.

StephanFowler
05-13-2011, 12:22 PM
So these discussions always seem to make my head spin (and I'm sure Dave will see my post and be somewhere between :bashhead: and :crying: ...sorry Dave)

Throw edge retention out the window for now....

Sharpness - for the sake of the discussion add an EP for consistency. Set the angle to "X" - could be 10, or 12 or... doesn't matter. And limit this to a 1k stone....no more, no less. Raise a burr on one side, flip the blade, push the burr to the other side, de burr with hard felt or cork, back to the EP, repeat to refine the edge, but still with only the 1k, and finally use the EP w/ 1k to strop.

Is a Forschner equally as sharp as a Shige, or Watanabe, Carter, Konosuke at this point? Each knife - exact same angle, stone, etc.
Are they or are they not all equally sharp? Why?

Now do the same with Blue #2, White, AS, CrMo, or PS quenched in virgin dew....aren't they still equally sharp?

OK - now change the scenario...this time what about Polish? If you start with two identical knives, and angles remain constant, but one is sharpened with the 1k, and the other is taken up thru the progression to a 5k or 10k....do you think one is 'sharper' than the other ? Why?



actually, potentially no, they would not get as sharp

when you abrade the surface of the edge you are removing steel right?
removing that steel makes the edge thinner, hopefully on a consistent plane equal and opposite to the other side (50/50 edge)
as the edge gets thinner those two planes will eventually meet, creating a "sharp" edge.

now, depending on the steel in question, the overall carbide size will determine how "sharp" that edge can become.
a steel with very large carbides CANNOT be sharpened as much as a steel with small carbides.

as the edge thins towards sharpness you will always eventually reach a point where the carbides are ripped out of the iron matrix, leaving ragged holes in the edge (on a microscopic level) with large carbides this is even worse.

if the carbides are sufficiently small and sharpening angle is not to aggressive you will be able to achieve an exact meeting of the two planes without losing the carbides, thus achieving a "sharp" edge.

tk59
05-13-2011, 05:12 PM
Tinh,

Here is a million dollar question. Can you pass your tomato test with a forschner? I understand that the edge may not last at all but can it pass it one time?

Well, I don't have a Forschner on hand BUT, I just sharpened a 4" Henckels Pro S on 1k Gesshin, 5k Gesshin, 8k SS and 0.5 mcn chromium oxide and it passed the tomato test with slightly more than the weight of the knife but it's a pretty small knife. I'm seeing a friend of mine in a couple days that currently has one of my Forschners. I'll see if I can get that back for a test, too.

Tristan, I find that sectional sharpening really helped me work on my consistency but I do a variety of strokes depending on what seems to be working. I think the direction I stroke affects the way the knife cuts significantly.

tk59
05-13-2011, 05:23 PM
actually, potentially no, they would not get as sharp

when you abrade the surface of the edge you are removing steel right?
removing that steel makes the edge thinner, hopefully on a consistent plane equal and opposite to the other side (50/50 edge)
as the edge gets thinner those two planes will eventually meet, creating a "sharp" edge.

now, depending on the steel in question, the overall carbide size will determine how "sharp" that edge can become.
a steel with very large carbides CANNOT be sharpened as much as a steel with small carbides.

as the edge thins towards sharpness you will always eventually reach a point where the carbides are ripped out of the iron matrix, leaving ragged holes in the edge (on a microscopic level) with large carbides this is even worse.

if the carbides are sufficiently small and sharpening angle is not to aggressive you will be able to achieve an exact meeting of the two planes without losing the carbides, thus achieving a "sharp" edge.

This is interesting, actually. I've been thinking about this a lot and trying to test it out and I've noticed a couple of observations I think might be worthy of adding:
1. Carbide size doesn't seem to affect the ability to pass the tomato test but it does seem to make it a bit more difficult AND it seems to make it through fewer times.
2. I really notice the difference when shaving and under the microscope. I have yet to have a comfortable shave with a knife made from stainless. Semi-stainless is a lot better, esp. the Heiji... :biggrin2: Shigefusa and Fujiwara Terayasu give the best shaves, so far, beating out the Heiji by a hair, maybe. It could just be my bias/preconcieved notion that carbon is going to be better, it was pretty close.

Lefty
05-13-2011, 06:20 PM
Hmmm. Are the stainless you're testing powdered?
Do you come up a bit at the end of your stropping like a straight razor user?

EdipisReks
05-13-2011, 07:32 PM
i've never gotten as good an edge with stainless, whether it be powered or non, japanese or swedish, as i do with carbon steel of any variety i've tried. same polish, same angles, just not as keen.

mikemac
05-14-2011, 10:27 AM
actually, potentially no, they would not get as sharp

when you abrade the surface of the edge you are removing steel right?
removing that steel makes the edge thinner, hopefully on a consistent plane equal and opposite to the other side (50/50 edge)
as the edge gets thinner those two planes will eventually meet, creating a "sharp" edge.

now, depending on the steel in question, the overall carbide size will determine how "sharp" that edge can become....

So, this is the intersection of geek knife user with geek knife maker? :biggrin2:

Lets limit this to a 1k stone and a 'reasonable' (?) 12* per side....are there any knives that we typically use where the steel carbides are large enough that they are getting pulled out?

StephanFowler
05-14-2011, 11:45 AM
So, this is the intersection of geek knife user with geek knife maker? :biggrin2:

Lets limit this to a 1k stone and a 'reasonable' (?) 12* per side....are there any knives that we typically use where the steel carbides are large enough that they are getting pulled out?


properly HT'd I don't know of any steels that would have carbide issues like that.
but again, that assumes properly Ht'd

very small variations in HT can have HUGE impacts on final carbide/grain size

one thing that I've been working on with 52100 is trying to find a balance between small grain/carbide size and hardenability.
It is not difficult to decrease the grain size to the point that the steel will not harden.
Annoyingly, the larger the grain size the easier it is to achieve high hardness (and typically blade failure as a result)

The holy grail for me ideally is to decrease the grain size to the point that I can just barely harden to 62HRC and then temper back very very slightly. If my understanding of 52100 is correct that will give me the toughest possible blade at the hardness that I want.

It's very easy to blow the grain up a little, HT to 64 or even 65 HRC and then temper back to 61, but the final blade would suffer due to increased carbide and grain size. It would show up as a blade that takes a good toothy edge at a very high grit but loses it very quickly.

a perfect HT (IMHO) takes a very high level of finish easily (this requires the smallest grain size possible) keeps it for a good while (which requires a fairly high finished hardness) and will not fail due to moderate edge abuse (tempered martensite is significantly stronger than non tempered martensite, thus the reason I don't reduce grain until I can barely harden the blade and leave it untempered)

tk59
05-14-2011, 12:15 PM
It is common for stainless steels to have enormous grain sizes in the tens and even over 100 microns due to the aggregation of chromium carbides. That's why properly HT'd AEB-L is a nice stainless. It has carbides on the order of 1 micron in diameter. That's also why powdered steels are generally stainless since it reduces the probability of the aggregation.

Tristan
05-14-2011, 01:35 PM
Well, I don't have a Forschner on hand BUT, I just sharpened a 4" Henckels Pro S on 1k Gesshin, 5k Gesshin, 8k SS and 0.5 mcn chromium oxide and it passed the tomato test with slightly more than the weight of the knife but it's a pretty small knife. I'm seeing a friend of mine in a couple days that currently has one of my Forschners. I'll see if I can get that back for a test, too.

Tristan, I find that sectional sharpening really helped me work on my consistency but I do a variety of strokes depending on what seems to be working. I think the direction I stroke affects the way the knife cuts significantly.

Today I took a long look at Jon's videos from the media section (all sectional sharpening), and then followed your advise on stropping. Loaded up the chromium crayon as much as the leather would let me smear on.

I must say that it is quite a nice edge! But of course, I made a wavy sharpening trail up 1/4 of the blade height... I still lack control.

I forgot to buy tomatoes. Tomorrow morning...

StephanFowler
05-14-2011, 01:41 PM
It is common for stainless steels to have enormous grain sizes in the tens and even over 100 microns due to the aggregation of chromium carbides. That's why properly HT'd AEB-L is a nice stainless. It has carbides on the order of 1 micron in diameter. That's also why powdered steels are generally stainless since it reduces the probability of the aggregation.


but not necessarily assumed,

to get even close to apples to apples comparison you need to take a stainless as HT'd by someone who has spent a lot of time and effort working on getting an exact process defined for their stainless.
take Butch for instance, I would bet hand's down that Butch's HT of cpm154 would blow away any production cpm154 blade. because production by it's very nature will optimize HT towards the least failure, whereas Butch has spent a LONG time optimizing HT towards performance.

I would bet good money that Butch's cpm154 does NOT have an enormous grain/carbide size. (can't speak from experience as I've never used one of his knives)

JBroida
05-14-2011, 01:43 PM
but not necessarily assumed,

to get even close to apples to apples comparison you need to take a stainless as HT'd by someone who has spent a lot of time and effort working on getting an exact process defined for their stainless.
take Butch for instance, I would bet hand's down that Butch's HT of cpm154 would blow away any production cpm154 blade. because production by it's very nature will optimize HT towards the least failure, whereas Butch has spent a LONG time optimizing HT towards performance.

I would bet good money that Butch's cpm154 does NOT have an enormous grain/carbide size. (can't speak from experience as I've never used one of his knives)

based on my experience with it, i would say it feels like a very fine grained stainless

Eamon Burke
05-14-2011, 05:24 PM
I have yet to have a comfortable shave with a knife made from stainless. .

Totally my experience here, but I had to say it.

I've had no trouble getting a comfortable shave, and I think it has a lot more to do with the prep you do on your face than the actual characteristics of the steel.

This is somewhat relevant, because the same goes with food prep knives--there is a point to which your knife's performance will require you enhance it's environment. Put a great knife on a cheap bamboo cutting board and sure, it'll have edge retention problems.

heirkb
05-14-2011, 10:51 PM
...I think the direction I stroke affects the way the knife cuts significantly.

I'm curious to hear a little more about your experiences with this. Do you find that doing certain types of strokes inherently lead to different cutting qualities (in your experience) or is it an issue of which stroke you're "better" at and therefore get a better result from?

tk59
05-18-2011, 03:15 AM
Tristan: Sounds good. Looking forward to seeing how it performs for you.
Stephan: I didn't say stainless can't be fine grained. I cited AEB-L and powdered steels as examples of stainless with small or fairly small grain size, in general. I think it is safe to say that most stainless knives out there are med to large grained steel.
Eamon: I'm not a razor/shaving guy (yet). Prepping the skin differently for one edge vs another would defeat the purpose. The objective is to evaluate the edge, not achieve a comfortable shave.
heirkb: I'm not ready to say anything really definitive but there does seem to be an effect. I'm planning on testing this on a pro chef. The problem is I need to acquire a stainless knife to test him with because I don't want to jack up the finish on my semi stainless stuff.

JohnnyChance
05-18-2011, 03:34 AM
Tristan, I find that sectional sharpening really helped me work on my consistency but I do a variety of strokes depending on what seems to be working. I think the direction I stroke affects the way the knife cuts significantly.

Makes sense though. I have noticed this as well. For a extremely exaggerated example, the way teeth on a saw are designed to cut in either a pull or push.

So for a gyuto that one push cuts with, you would want to sharpen in one direction, and in say a suji, where you are making long pull cuts, the opposite way.

tk59
05-18-2011, 03:49 AM
Makes sense though. I have noticed this as well. For a extremely exaggerated example, the way teeth on a saw are designed to cut in either a pull or push.

So for a gyuto that one push cuts with, you would want to sharpen in one direction, and in say a suji, where you are making long pull cuts, the opposite way.

Yeah, I think that's what I'm getting. I'm also thinking that a one-handed sharpening would yield a better all around edge than one that has been sharpened by switching hands. Again, I think I want to test this on an unsuspecting cook/chef and see if he notices. I'm afraid I might be "wanting" to see a difference and I'd rather eliminate that bias.

JohnnyChance
05-18-2011, 03:57 AM
You should try to get 2 or 3 identical knives, sharpen them differently, mark them, and let testers try them blind.

tk59
05-18-2011, 04:20 AM
Yup. That's more or less the plan. Too bad you don't work nearby. You could be one of the guinea pigs. :biggrin:

StephanFowler
05-18-2011, 11:16 AM
Stephan: I didn't say stainless can't be fine grained. I cited AEB-L and powdered steels as examples of stainless with small or fairly small grain size, in general. I think it is safe to say that most stainless knives out there are med to large grained steel.

Oh I agree, I was just trying to further the discussion along a path that generally doesn't get exposed when the discussion turns towards stainless vs. carbon

I hate to see stainless all lumped together when there are truly spectacular examples available.

MadMel
05-19-2011, 12:31 PM
Stephan: I didn't say stainless can't be fine grained. I cited AEB-L and powdered steels as examples of stainless with small or fairly small grain size, in general. I think it is safe to say that most stainless knives out there are med to large grained steel.


Hey on this line of thought, has any one had a Global suddenly chip on them while sharpening? I had this experience once and it scared the **** outta me cause I thought I damaged the knife or something. I later heard that it was due to the carbides of the steel being large grained and was wondering if this is the case?

tk59
05-20-2011, 02:28 AM
How big was the "chip?" What stone were you using and what angles were you sharpening at? That explanation doesn't really sound reasonable to me. I'd guess it's more likely a defect in the blade.

MadMel
05-20-2011, 02:42 AM
How big was the "chip?" What stone were you using and what angles were you sharpening at? That explanation doesn't really sound reasonable to me. I'd guess it's more likely a defect in the blade.

I was using a Naniwa SS 5k. In preparation for going onto 10k.. I can't give an accurate number on the angle. I'd assume about 18 degress give or take the spine was prolly 3-5 mm off the stone. And the chip was not very big, about 3mm across. Thing is, it happened a few times, at different places along the edge. Good thing it was during some sharpening training that I did at a pro's shop.

tk59
05-20-2011, 02:50 AM
Hmm. In my book, 3 mm is enormous... Large carbides might be around 0.1 mm across. That really doesn't sound right to me but I'm no expert. Really wierd. Was the owner surprised or did he think it was pretty normal?

MadMel
05-20-2011, 02:56 AM
It was actually a blade that was sent for sharpening to the guy that I'm practising my sharpening skills with, so the owner was not present. But according to the pro, it is not the first time that this has happened to a global. And I agree that 3mm was pretty large so I was kinda stunned.. He says that usually, the chips are not so large but still large enough to be seen with the naked eye. And I think the 3mm was a 1 off cause after that, I did see some shiny metal bits come off now and again but nothing as large. In the end, he did a 20* angle on it and also added a micro bevel...

Seb
05-20-2011, 04:51 AM
3-5mm off the stone for a Global is pretty extreme, in my book!

MadMel
05-20-2011, 10:35 AM
3-5mm off the stone for a Global is pretty extreme, in my book!

Yeah that's what I thought when it happened. Tho 3mm off any knife without a visible defect is pretty extreme in any case.

Cadillac J
05-20-2011, 11:19 AM
Global steel is so gummy and tough, that I am very surprised it could even chip like that...especially on a 5K stone?

I sharpen a G-2 that my girlfriend uses with less than a 20 degree angle, and there have been no problems at all (and she goes hard with it). So your issue doesn't seem common in my experience.

MadMel
05-20-2011, 11:54 AM
Hmm maybe it was just a bad shipment?

mikemac
05-20-2011, 12:03 PM
Globals are also among the most counterfeited...

MadMel
05-20-2011, 12:13 PM
Globals are also among the most counterfeited...

I didn't know that... How do you tell if it is a real global?

tk59
05-20-2011, 12:16 PM
good question. i didn't know that either.

Eamon Burke
05-20-2011, 12:18 PM
Carbides are not that big. Large carbides break off in larger clusters than finer grained steel, and you can feel it, but you need some magnification to see any difference.

Did you see it break? And did it break off in one piece that you found? How fast were you moving?

I ask because it's possible that you were abrading the knife against an edge of the stone due to improper pressure and/or dishing and actually ground the "chips" into the blade without noticing.

MadMel
05-20-2011, 12:39 PM
Yup I saw it break. The way I was sharpening was the way it was shown in Jon's vidoes. I was not moving fast at all by any standards, in fact I was moving slower then Jon did in his vids cause I'm still kinda getting a feel for it. The stones were pretty flat so i don't think dishing was an issue. The break actually occured when I ran my fingers across the blade like that: http://www.cookware-baking.net/_cache/Carving%20Knife/img/kitchen_knife_sharpener_2.jpg
I was doing that when a piece came off in my fingers...

tk59
05-20-2011, 12:53 PM
Crazy... Sounds like a lemon to me.

JBroida
05-20-2011, 03:16 PM
either you ground the edge too thin (which is not what i think based on this thread) or that knife has issues

Eamon Burke
05-20-2011, 05:09 PM
yeah. send that thing back. sheesh. talk about mass production quality control--a knife that didn't even get rubbed before it shipped.

mhlee
05-20-2011, 05:21 PM
That's not a finish issue, that's a defect issue. I've had a Global G-2 for close to ten years and it has not had a significant chip once.

That steel is so friggin tough (which is why it's a PITA to sharpen well). I've used it to chop/hack through all kinds of chicken bones, fish bones, cartilage, etc., and it's survived them all. It's even gone through a old plastic/fiberglass countertop. No chips in the edge like you're talking about.

mikemac
05-20-2011, 05:58 PM
I didn't know that... How do you tell if it is a real global?

...from a couple of Google articles....where'd you buy it and how much did you pay - big discounts and auction buys are one indicator. Block sets and /or chef roll's are another. The Dimples - real Globals use a dark color metal for the dimples, not paint, the logo's should be etched, not painted, and apparently Gobal Professional was only sold in Japan...but google it for for info.

JohnnyChance
05-20-2011, 06:16 PM
...from a couple of Google articles....where'd you buy it and how much did you pay - big discounts and auction buys are one indicator. Block sets and /or chef roll's are another. The Dimples - real Globals use a dark color metal for the dimples, not paint, the logo's should be etched, not painted, and apparently Gobal Professional was only sold in Japan...but google it for for info.

I have to deal with making sure sneakers arent fake...now I have to make sure my knives arent either! Yeesh!

TB_London
05-20-2011, 06:50 PM
I've seen quite a few fake globals and it's quite easy to tell if you've ever used a genuine one, they look wrong, the steel has a different shine to it, the handle finish is dodgy, they just feel wrong.

The chipping may have been caused by small cracks near the edge from misuse, that as you thinned the edge from sharpening weakened it enough to chip? Just a theory.....

dmccurtis
05-20-2011, 08:00 PM
I've had it happen a few times to Globals. My guess has been that it was the result of a small dent or deformation that because of the steel's toughness didn't chip out immediately, but wore thin once sharpened into.

MadMel
05-21-2011, 03:21 AM
That's a bunch of reasons to consider. I think curtis's reason may come pretty close to the truth, although maybe it was also due to bad QC on this particular shipment.

Tristan
05-21-2011, 07:21 AM
I just sharpened up two defunct globals thanks to this thread... and the 'flexible' utility knife ate my fourth finger on my left hand. Sheet, it tingles as i type this.

The 20cm chef and the petty (in this forum's speak) both were kinda weird on my choseras.

I had these strange particles in the swarf, like tiny grits. Sounded awful on chosera stones too, usually there is a very pleasant sound when I go to it. Very scratchy sounding. But in the end, other than a few scuffs I made due to my inconsistent angles, nothing came off. And I was fixing a rolled edge at one point of the chef - My friend's mother used it for a while on loan, I think she must have chopped at a chicken pretty vigorously. Still didn't chip off. The edge realigned after some time on the stones.

Quite sharp edge too, just not as satisfying as sharpening a nice carbon blade.

Seb
05-21-2011, 09:34 AM
I have a Global 18cm chef's and I have got it pretty damn sharp, if I do say so myself. It's just that the geometry sucks - it's fat. And I never use it, it's in my knife bag on the shelf up high. lol

But I have the 15cm flexible utility and I like it as a pineapple or mango knife. Very very thin.