JAPANESE KNIFE - Edge Geometry 101
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- Опубліковано 8 січ 2021
- Hey folks, thanks for tuning in as always!
In todays video we're going to talk about something some of you are aware of, and always comment about when its touched on, but we still feel like edge geometry gets forgotten for people being too worried about steel type, or weight, or HRC. In our opinion the geometry makes as big if not bigger of a difference than the rest of those! We'll go over the basic grinds you'll find on most Japanese knives here but if you want to know more about some more specialty grinds leave a question in the comments below, if we get enough requests well make an Edge Geometry 102 to follow this up!
Also stay tuned for our next video where well be discussing how to thin your knife the right way to keep it cutting the way that it was meant to after years of sharpening up the blade!
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Thank you for the super informative and well explained content!
I’m always enjoy watching your videos
Yes! The last piece of concise information i needed to understant the general picture when looking for a knife for a specific use
Thats great to hear, thats why we do it!
Nice descriptions! Looking forward to the next episode!
Thanks Ether, just got finished filming the thinning video. Editing time!
Thank you Gage for another useful video!
Clear and informative! Thanks! A not so very skilled home cook like me might want to have one of those hollow/concave knifes, but probably should get the convex one for the durability.
No matter how far along you are in your culinary journey it will not be easier to learn to handle a thin knife down the road. I think knife care and maintenance should be one of the building blocks of cooking!
@sharpknifeshop thanks for all the great content! Especially this one is very informative and maybe a bit overlooked (?) I was thinking about sharpening, I have a flat grind on two of my knives (Yoshikazu Tanaka bunka and gyuto). My question is, if it's any difference when it comes to the sharpening angle compared to a hollow grind? I guess 15° applies on harder japanese steel anyways. Thanks alot!
Great video!! Good information
Glad it was helpful!
That was wicked good!!
Thanks Trevor, glad you liked it!
This is the type of specialized info, that makes me go, 「あぁ、なるほど！」Hahaha
This dude is high as a Georgia pine. haha good video.
Nice explanation of how the various grinds are made - I had wondered about this! Re geometry - blade thinness is an important factor too, e.g a thin convex knife may perform better than a thicker flat one.
Also, on the unusual grinds list - I have a Tanaka blue#2 with left side dead straight (like a single bevel) and right side convex. The secondary bevel is however 2 sided. It is magic (I'm right handed, which I suspect is important here), this is probably my favourite grind (sadly not common - I have a Tanaka VG10 and it is convex on both sides, so not sure if they are doing the unusual grind any more).
That is a pretty unique grind, I've seen videos of old school Chinese chefs doing this to their cleavers to almost mimic that of a single bevel, with less steering from the double bevel at the secondary edge. Ive also seen a lot of honesukis that are ground in this way (obviously still hollow on the back) and they don't steer as much but they take a scary sharp edge that way!
In the interest of being correct, had a good look at my Tanaka VG10 and it *is* in fact completely straight on the left side and convex on the right. So they *are* still doing that grind. Not as obvious as the blue#2 due to the convexing being gentler so the whole knife is easily confused with either a 2 sided flat or convex grind. Anyway, my favourite geometry!
In my experience, flat grind (full flat) offers a very poor food release, compared with a convex grind... I use a miyabi kaizen II gyuto, and food sticks a lot on the blade, whereas my old western style knife, that is very convex, does not cause as much of sticking...
Yeah, definitely the worst for food release but they can make for some super thin lasers that cut like an absolute dream. Its always a trade off.
@@SharpKnifeShop In this regard I don't really get your point if you place the flat grind as best for food release, as well as the worst... I would consider convex or S grinds the most efficient at avoiding sticking... (not having ever tried a hollowed blade yet)
Keep in mind that flat grinds, and full flat grinds are very different. And in our experience food release is really only an issue on firmer ingredients like potatoes or carrots or things like that, that being said if you're cutting things paper thin they'll become flexible and stick to convex grinds a little more than the hard angle between the two bevels on a flat ground, at least in our experience, which is why we picked that!
@@SharpKnifeShop What does full flat vs flat grind mean?
@@quintinspina4270 full flat grinds are where the entire face of the knife is the bevel.. from the spine down to the edge. whereas a flat grind can be tall or short, it can be 5 mm or 10 mm or any mm... just that it's FLAT. meaning like the sides of a triangle. Some knives have shorter flat grinds and some have taller flat grinds. If the grind is so call it goes all the way to the top of the knife, aka the spine then it's full flat grind. The taller the flat grind, the thinner the edge can be but the worse the food release. Shorter flat grinds wont be as thin but can have better food release. Anyway, convex grinds are honestly the best especially for kitchen knives. They are thin where it counts but also more robust and durable than flat grinds and they literally push things away so they have much better release. The issue is they are hard for average users to maintain. it's much easier to maintain a flat bevel because you can just lay it down on a stone and grind.
What about a very thin convex grind ? Like a Tojiro Pro R2 ? I've found they feel very nice moving through potatoes and such
Man I have so much anxiety about working with my first hamaguri sharpening process in order to maintain that lovely geometry the knife came with. I just got my first knife with a wide bevel and I'm very confident sharpening in simpler ways but it's so hard to tell if I'm doing this well when it just starts with loooooots of immediate ugly scratches.
Just remember to take your time with the first few strokes and flatten very often and youll be fine!
Great content & outstanding explanations with a down to earth approach to understanding knife design. I eat a lot of sweet potatoes; make knives & experiment with knife design. Just thought I would share my insights. Concave grinds cannot be significantly thinner behind the cutting edge than thin full flat ground blades. Lateral stability of the blade requires dictates a minimum thickness behind the cutting edge. Hollow grinds compete well with thin flat ground blades until you get into cutting high density vegetables like sweet potatoes. In these cases the thick portion of the hollow ground blade engages & they become hard to push.
Thank you so much for your comment Daniel, we really appreciate the support and the extra insight you've provided here. Great stuff!
One thing is though. You can change your edge geometry. You can not change the steel your knife is made from. so steel still matters, just not nearly as much as newbs think. steels is used as gimmick and marketing point. but the steel isn't what's costing money, its the expertly executed grinds on the better knives. it costs more to grind thin and takes more skill and time. Another thing is, unless the knife has the right geometry then there is literally no point in using some gimmicky fancy steels because a knife with basic steel and better geometry will still cut vastly better and for longer. Obviously the best is to have a knife with excellent steel and excellent geometry. Then you get it all. You get a tough durable edge that can stay keen and maintain cut initiation for a long time, but also a knife that's sharp because of the geometry and would continue to cut well even after the edge itself is dull and that cut initiation aka bite is long gone. Geometry is what cuts. edges are keen, blades/knives are sharp.
Have you tried an S grind and does it really release food better?
I have tried an S grind and it had a pretty pronounced thickness above the edge that I had to take down a fair bit, that being said after this was done I really do like the performance of it and its fun because I sharpen the secondary bevel really high like a scandi grind. Its certainly more work to sharpen and I wouldnt say it performs any better than a hollow grind in terms of food release, but its a labor of love and a super fun knife!
excellent point. but its still hard for newbs to really understand this until they get experience for themselves. edge geometry is 100% objectively and factually more critical than the steel choice. even if you com-are the two most different steels used in these kinds of knives. True traditional single bevel knives are way under rated. Some of my favs are chisel grinds and traditional single bevels.
Many thanks. I also found myself wanting the AS steel as well. I purchased a Takeda guyoto, with a scandi grind, what a pain in the ars this thing is to sharpen, (Just my opinion). The biggest problem I have is following the original angle with a bench stone, and of course, it has to be finished on a fine grit for the full affect (I use a black Ark 8" X 3 X 1). Any tips would be greatly appreciated. Maybe I am doing something wrong. (I started sharpening 55 years ago, so I'm not new to cutting myself (lol)).
I miss a thinning ease category, respectively how easy different styles of grinds are to thin out while retaining the grind style.
I'd imagine that convex is close to impossible to retain its "convexness" using standart home equipment, concave is doable but needs more precision in technique, and flat would be the easiest?
Not quite! While you COULD do a convex grind on a whetstone, which I imagine is what everyones sharpening on at home because not that many people have belt grinders, especially the ones that don't have a hard backing behind the belt, it would require a motion that I imagine impossible to do well freehand without spending hours and hours on it. As for a hollow ground the only way to get that is to use a wheel as you cant scoop material out of the centre point with a flat abrasive. Should you want to follow the bevel with a radiused block of wood and sand paper Im not gunna try to stop you. But I think youll quickly see how difficult it is to remove that material by hand, even on a stone.
For sharpening convex on whetstones are retaining the "convexness" use a loose wrist. Watch some bushcraft knife channels for sharpening convex as that and scandi grinds are used exclusively, they continually sharpen convex knives while retaining the geometry and not flattening out a convex blade.
Gabe practices to throw the holy hand grenade.
Its Gage :'(
You mentioned an S-grind. Is that real, and if it so, how is it possible? That just doesn't make any sense to me.
An S-grind is a compound grind that’s exactly how it looks like. The hira or blade face is convex, the blade road leading to the edge is hollow. Like an S
@@agentKx2 isn't it the exact opposite? The main body of the blade is hollowed and the cutting edge is flat, or lightly convex?
@@maximeregamey4458 I went back and re-researched it. Turns out we’re both right, you’re just more correct! I was looking at the “S” from the left face, while it’s supposed to be on the right face. What I was referring to turns out to be a “reverse S-grind”
@@agentKx2The name is not intuitive indeed... I can't find an exemple of a reverse S grind though... I may be wrong here but isn't it just a name to describe the same thing? The reverse could mean that you have to look from the right of the letter S? I you have an exemple I would gladly check it out, I'm curious now!
@@maximeregamey4458 Yeah you’re probably right, because the S grind literally refers to either case, so I guess it defines both upper and lower hollows? Here’s a Custom Haburn AEB-L Gyuto with an S grind on the bevel:
www.kitchenknifeforums.com/threads/review-ian-haburn-240-aeb-l-custom-gyuto-vs-kato-workhorse-beauty-and-the-beast.20297/
And I believe Kamon Knives makes some of these as well!
other than japanese kitchen knives and straight razors, every single hollow grind knive I've ever seen in my knife has been absurdly thick behind the edge. just because it's got a hollow grind doesn't mean it's thin, most of these knives have MASSIVE secondary bevels you can see from the moon. hollow grinds are "good" because they look cool and also you can use thicker stock... but 99% of the time these knives get a hard pass from me. to be avoided. also I only see hollow grinds on the cheapest Japanese kitchen knives, basically stuff you should avoid anyway like Masakages and other stuff like that. I will say I have a nigara that have an expertly done hollow grind on it and that thing is an absolute laser beam. It's less than 10 thou thickness behind the edge at the thickest point and the tip is nearly half that.
What is medium grind
Unless this is something we said in passing during the video, in which we would have been referring likely to a medium thickness grind, I don't believe a medium grind is a thing.
Don't forget about heat treatment, HRC matters.
Of course it does! But more often than not we see people getting into Japanese knives go off nothing other than the HRC, and that ain't right either!
@@SharpKnifeShop It gets wonky pretty quick. I've got no problem with Aus8 or VG10 running at 58-60 HRC on a kitchen knife, but something like Hap 40 under 60 HRC is just a waste of steel.
Convex vs conVEX 😂