Thinking I got a way too sharp an edge on this one? Actually, I intended to give this thick blade a shaving sharp edge. I may even shave with it tomorrow. This is how a properly worked blade should look for duty.
Can a knife blade be too sharp?
- Thread starter rodrigaj
- Start date
Remember that almost all knives have more complex, compound geometry than plane blades. And in the case of some higher end kitchen knives - considerably more complex.
When you sharpen a plane blade ‘normally’ / without a microbevel, you do it with the main bevel flat on the stone. When you sharpen a knife ‘normally’ you do it with the main bevel raised off the stone.
In this way sharpening the edge of a knife is already analagous to putting a microbevel on a plane. Putting a microbevel on a knife is like putting two microbevels on a plane.
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In answer to your main question - this response is an extremely good summary:
A knife edge can certainly be too polished, to too high a grit for what you’re trying to do. And will literally cut things less well than the same blade finished lower.
It kinda depends how you define ‘sharp’. But if you define it as how well it cuts what you’re wanting to cut, then the higher grit edge is less sharp in that scenario.
So as @AimlessWanderer said - no, (imo) you can’t really have a knife edge that is ‘too sharp’, but you can have one that is sharp in the wrong way. ‘Sharp’ isn’t really a property of the blade itself, it depends on what you’re cutting too, because everything about how something cuts something is about friction. And that depends on the properties of both things.
For a closer look at all that, here’s a post I wrote a while back:
Different kinds of 'sharp'
This is an amalgamation of a few posts I've made in various threads to explain a bit about sharpness in relation to razors and knives, because I think it's quite an important thing to understand when using, and especially honing different kinds of blade. Sharpness is not an absolute...
www.badgerandblade.com
Cutting blades are designed according to the end use. The edge of an axe, milling machine bit, wood plane, chisel, hunting knife, combat knife, chef knife, sushi knife, surgical scalpel and razor serve different purposes. Their design will vary depending upon the function. One thing that I always found interesting is that a rope composed of multiple strands and fibers is more easily cut by a knife with a serrated edge than one with a smooth edge, even if it is quite sharp. For this reason, many knives are designed with a combination blade that is smooth at the front half, but serrated at the rear. Serrated knives cab also be used for slicing tomatoes and cutting up steak.
I have a cleaver knife that has a wide, heavy blade that makes it good for chopping meat and could be used as a camping knife for splitting kindling, etc. However, that would not be my knife of choice for slicing an onion or filleting a fish.
The best edge is the one that is best suited for the cutting task at hand. If I am shaving, I want my blade to have a super sharp, super smooth edge, but such an edge would not be well suited for other tasks. If you are preparing sushi, you want your knife to be super hard, super thin with an acute angle and sharpened on a ultra fine grit stone, but that edge would be far to brittle for many other tasks.
I have a cleaver knife that has a wide, heavy blade that makes it good for chopping meat and could be used as a camping knife for splitting kindling, etc. However, that would not be my knife of choice for slicing an onion or filleting a fish.
The best edge is the one that is best suited for the cutting task at hand. If I am shaving, I want my blade to have a super sharp, super smooth edge, but such an edge would not be well suited for other tasks. If you are preparing sushi, you want your knife to be super hard, super thin with an acute angle and sharpened on a ultra fine grit stone, but that edge would be far to brittle for many other tasks.
Lot of good comments. I think edge angle is critical, but I don’t even think of that as a factor in sharpness - you can make an axe edge super sharp with a 45 degree included angl.
To me grit level is more a focus nowadays. For example just sharpened my yanagiba today (sushi knife) and a big question in my mind was where to stop on grit progression. I ended up stopping with a hard (not true hard) Ark. We will see how it goes tomorrow when it meets up once again with my homemade gravlax. This morning it didn’t do that great, thus the trip to the stones.
For my main kitchen knives I do mostly push cut rather than slice, so in theory I ought to go sharper, but lately I’ve been just finishing with a Washita and that works fine.
I will say that the MOST critical item for getting a sharp edge is maintaining a strict bevel angle, regardless of what that angle is. I’m mostly free hand sharpening, but my best free hand work is still a shadow of what I can do with my EdgePro Apex. And that is true of all edge types, including the convex edge I put on a hatchet last year. In fact I might argue that an EdgePro (or equivalent system) is even more useful when the goal is to make a convexed edge than a flat bevel edge because you have the edge angle control to change the angle accurately in very small steps.
To me grit level is more a focus nowadays. For example just sharpened my yanagiba today (sushi knife) and a big question in my mind was where to stop on grit progression. I ended up stopping with a hard (not true hard) Ark. We will see how it goes tomorrow when it meets up once again with my homemade gravlax. This morning it didn’t do that great, thus the trip to the stones.
For my main kitchen knives I do mostly push cut rather than slice, so in theory I ought to go sharper, but lately I’ve been just finishing with a Washita and that works fine.
I will say that the MOST critical item for getting a sharp edge is maintaining a strict bevel angle, regardless of what that angle is. I’m mostly free hand sharpening, but my best free hand work is still a shadow of what I can do with my EdgePro Apex. And that is true of all edge types, including the convex edge I put on a hatchet last year. In fact I might argue that an EdgePro (or equivalent system) is even more useful when the goal is to make a convexed edge than a flat bevel edge because you have the edge angle control to change the angle accurately in very small steps.
Knife and razor edges are very personal, for me personally you can never have a knife too sharp, the most important is what angle you choose, for an everyday EDC knife I will go with a 20-degree angle that's a combined 40 degrees at the apex, also the most important thing to remember that it's only steel and people seem to forget Extreme sharpness is ephemeral!
These are interesting comments, and correct in one way, though perhaps not quite the whole story...
Apart from finishing grit, the thing that really, really influences perceptions of 'sharpness' is the total edge angle and how thin a blade is just behind that. How low an angle a particular steel will hold an edge does depend on hardness certainly, but also on stuff like carbide structure. It's perfectly possible to make softer steels quite incredibly 'sharp', and a lot of super-duper hard steels don't take very good low angle edges. For kitchen knives the sweet spot seems to be in the 60-63 HRC range ime, the Japanese 'paper steels' are still pretty much the best in the biz imo.
And for sushi knives they don't actually traditionally use the hardest of them - most yanagiba are made from shirogami (white), rather than the slightly harder Aogami (blue) steels. In this instance it's the softer steel that takes a high grit, more polished edge better, while aogami edges tend to have more teeth and better retention.
That should work well I'd have thought, especially if the surface was a little burnished. Yanagi edges want to be extremely similar to razor edges - very fine, quite slow, and not too soft stones are where you want to be.
The late, great Vadim Kraichuk, PhD — who did knife-sharpening research as extensive as anyone I'm aware of — called this notion a myth. You can certainly sharpen at too shallow of an angle, and you can certainly put enough polish on an edge that cut initiation seems to suffer (especially at steeper angles), but you can't get the edge "too sharp", at least according to Kraichuk.
His book, Knife Deburring: Science behind the lasting razor edge, is the most informative material I've ever read on knife sharpening. English wasn't his first language, and I think he would have benefited from having a professional writer help him with the wording and organization of the book, but the information contained within it is unparalleled. In case anyone is considering it, he comes at knife sharpening mostly from a Tormek perspective, but applying his ideas to freehand sharpening paid significant dividends to me.
His book, Knife Deburring: Science behind the lasting razor edge, is the most informative material I've ever read on knife sharpening. English wasn't his first language, and I think he would have benefited from having a professional writer help him with the wording and organization of the book, but the information contained within it is unparalleled. In case anyone is considering it, he comes at knife sharpening mostly from a Tormek perspective, but applying his ideas to freehand sharpening paid significant dividends to me.
Even soft steel can take a fearsome edge but soft steel edges won't last long while doing any work. If it's just mild steel, the edge may fail during the first use. I like to think about old, old, butcher knives, not hard at all, maybe a slightly higher carbon steel is used. Probably not 1095 spring steel but maybe 1040 or something in that range. The small amount of extra carbon over plain, cold rolled steel, gives it a little more edge endurance while allowing steeling to keep it going during use.
A thing I've noticed at work is the difference between D2 and cpm3v. If the die clearance goes away and the parts start to touch, the D2 part will get worn by the cpm3v. The cpm parts are unimpressed by the D2 steel and don't sustain any damage. However the cpm is a PITA to resharpened. It fights you all the way, making the grinding wheels smaller while creating heat. If you try to crowd it while grinding, the heat build up (even in a big surface grinder, 12 inch wheel, with coolant) will damage the surface and cause chipping during use. You can easily burn it so bad you can see the surface fractures. It's the ones you don't see that cause problems.
I hollow grind plane irons and my better woodworking chisels on a water cooled Tormek, then dress them as needed until they need to be hollow ground again.
- Thread starter
- #30
Very interesting comments.
Re the angle: Can one assume that the factory angle that the knife comes with is a good EDC knife angle? (Thinking of Benchmade Knives, mini's)
Re the angle: Can one assume that the factory angle that the knife comes with is a good EDC knife angle? (Thinking of Benchmade Knives, mini's)
It will likely be a conservative choice. If you're doing aggressive things, things that might chip a knife at a lower angle, it may be about right. If you're doing more slicey things, you may want a more acute angle. I usually make the angle a bit lower.
I use two methods for keeping my EDC knives sharp when I don’t use the stones. I have two pocket sharpeners: carbide and ceramic V 20 degree.
I also have a hollow ground carbide piece welded into a steel handle with a soft plastic handle cover and cap. I had these made up years ago after seeing one in a lumberyard. They work great for putting on a final edge…..light strokes at an angle along both sides.
I also have a hollow ground carbide piece welded into a steel handle with a soft plastic handle cover and cap. I had these made up years ago after seeing one in a lumberyard. They work great for putting on a final edge…..light strokes at an angle along both sides.
100% this. Manufactures choose bevel angles to minimize complaints and warranty returns, not to maximize performance.
May i ask how you like the Tormek? I have a T1 coming as I'm tired of sending out my kitchen knives for sharpening.
Thank you,
Mike
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