edge geometry

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noob93

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Feb 6, 2016
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So awhile ago I was In a big knife store fondling many knives and one thing I found was regardless of price point many suffered from poor edge geometry. I would say 90 percent that had poor edge geometry were often times simply too thick to cut well. To my surprise this included many 200-350 dollar knives. Im speaking of production knives here of course. Im not going to start a war and name the specific companies as I know most have many fans on here. I will say though out of all the fixed blades I handled the cheaper bucks and the like had very good edge geometry,compared to others with higher price tags and better steel. Its funny to think that some of those companies using such "superior" steels had big thick grinds. Now I get that many people abuse knives (Iv been guilty on more then one occasion).At some point does it not just become silly to make a knife with such a great steel with poor edge geometry?
 
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Some validity with what you said. But it all depends on what the knife is meant for, vs how you use it. There are some knives with very thin stocks that are super thin behind the edge which are meant more for slicing tasks, while a huge majority of fixed blades are made for chopping and to withstand abuse. Also, the cheaper the knife, the thinner I'd expect the stock to be in some cases, since more metal = more cost to produce. One more thing to understand, is if we are talking purely on fixed blades, if you use a higher end stainless steel, I'd PREFER a thicker stock, since higher end stainless steels are oriented for edge retention and their stainless abilities with poor toughness.
 
I think that both of you are right... Whew!
Many of the folders in the price range of $200 and up do seem to come with blades that are often 0.160" thick, and greater. For casual use, this is not my cup of tea.
Certainly, the Sebbie 21's have done quite well with 0.125" for a long time. My Zaan is 0.140" and I have used it hard with no troubles.
I am NOT a fan of thick steels, and recently had REK do a regrind on one of mine that was NOT a slicer...and NOW IS.
 
Most mfg's err on the thicker side because they don't want to have warranty/replacement issues I would guess... I agree with you, most production and many customs out there are simply ground way too thick for their designed purpose. The OEM's and many users don't push the geometry to the limit to find out a knife can handle to gain the max performance out of it. Each knife should be dialed in, geometry wise, to the hardest task it will likely see. So for example, if you will strictly be slicing cardboard you could go w/ a zero grind or something that will be more fragile. If the hardest use was to stick your blade under a zip tie and twist to cut it, then you need something thicker such as say .010" thick at 15 dps or so. If you will be chopping green wood you will need something like .025"-.030" thick at 15 dps, and seasoned wood .035-.040" thick to handle those respective tasks without any fragility issues. Note that these are general guidelines and not hard rules.

Me... I like to push mine to the limit. But it's because 1. I don't have high end knives and 2. I'm not afraid to break what I have because I can likely fix it :D
 
`br4dz- said:
Some validity with what you said. But it all depends on what the knife is meant for, vs how you use it. There are some knives with very thin stocks that are super thin behind the edge which are meant more for slicing tasks, while a huge majority of fixed blades are made for chopping and to withstand abuse. Also, the cheaper the knife, the thinner I'd expect the stock to be in some cases, since more metal = more cost to produce. One more thing to understand, is if we are talking purely on fixed blades, if you use a higher end stainless steel, I'd PREFER a thicker stock, since higher end stainless steels are oriented for edge retention and their stainless abilities with poor toughness.
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Yup I absolutely agree that different fixed blades are meant for different things. Of course the cost would be indicative of the stock on budget blades generally. I'm not only referring to fixed blades but staying on that subject I don't see the need for a 4 inch blade to be ground like a 9 inch blade. I agree there is a stigma with poor toughness surrounding stainless steels but surely cpm 154 or s35vn is plenty tough for a 4 or 5 inch blade. Alpha knife supplies has cpm 154 listed as tougher then a2 last I checked. I'm not even referring only to stainless either there were some offerings in carbon steels like 1095 or 5160 even that were very thick.
 
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Sonnydaze said:
I think that both of you are right... Whew!
Many of the folders in the price range of $200 and up do seem to come with blades that are often 0.160" thick, and greater. For casual use, this is not my cup of tea.
Certainly, the Sebbie 21's have done quite well with 0.125" for a long time. My Zaan is 0.140" and I have used it hard with no troubles.
I am NOT a fan of thick steels, and recently had REK do a regrind on one of mine that was NOT a slicer...and NOW IS.
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Yes folders I don't get at all. I mean I don't care how strong the lock is I'm not gonna beat on a folder PERIOD unless my life depended on it. Often times those knives get marketed as hard use thus making up for the fact that they can't cut crapola. Seriously how many guys are really batonning and chopping with their folders? Me personally I like my fingers just the way they are.
 
razor-edge-knives said:
Most mfg's err on the thicker side because they don't want to have warranty/replacement issues I would guess... I agree with you, most production and many customs out there are simply ground way too thick for their designed purpose. The OEM's and many users don't push the geometry to the limit to find out a knife can handle to gain the max performance out of it. Each knife should be dialed in, geometry wise, to the hardest task it will likely see. So for example, if you will strictly be slicing cardboard you could go w/ a zero grind or something that will be more fragile. If the hardest use was to stick your blade under a zip tie and twist to cut it, then you need something thicker such as say .010" thick at 15 dps or so. If you will be chopping green wood you will need something like .025"-.030" thick at 15 dps, and seasoned wood .035-.040" thick to handle those respective tasks without any fragility issues. Note that these are general guidelines and not hard rules.

Me... I like to push mine to the limit. But it's because 1. I don't have high end knives and 2. I'm not afraid to break what I have because I can likely fix it :D
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Great post Josh with many good points. I do get that warrantee is an issue and people misuse their tools. With that said there has to be a sweet spot where a knife is still tough but cuts well. I do admire your grinding and sharpening skills. Must be nice to get the absolute most out of your knives. Just out of curiosity how many high end knives would you say are ground properly for what they were meant for? I ask you this as I'm sure you see quite a few come in for regrinds.
 
It is a dirty rotten secret of good marketing that most consumer products are meant to be sold, not to perform.

Thicker blades have a better emotional allure for many buyers. Thicker means tougher means better in this line of thinking. When I used to work retail in outdoor gear, we would call such designs "easy to sell".
 
I'll just chime in to say I feel your pain Noob93.

I have a decent sized collection of both high-ish end Spydercos and Bussekin, but just accept that the edge geometry is going to be sort of a crapshoot in terms of being in line with my personal preferences because I favor the designs. Though I believe Spyderco has been trending towards thinner grinds lately, I've received a few head scratchers from them. I do understand the pratical issue that manufacturers have to protect themselves against warranty problems as well.

I've been slowly building up my competence with reprofiling and regrinding, which has been a big help. I've practiced a lot on my 1x30" with very cheap knives, MTech, etc... and it's funny how I'll sometimes grab those $10-$15 regrinds over much "nicer," more expensive blades simply because they cut so much better and, like Josh said, I don't have any concerns about damaging them.

As an aside, I also thought experimenting with very cheap knives would be an interesting baseline to have a comparison against higher end production steels and heat treats. In general though, I haven't been able to tell much difference between how "good" or "bad" steels perform in use at all. The conclusions I've drawn are that, for me, geometry/cutting ability and ease of sharpening trump most other factors in the user blades I favor the most for moderate to heavy use. For light use edc blades, I just carry whatever I want to on any given day because geometry, etc aren't overly critical to accomplishing menial tasks.
 
pinnah said:
It is a dirty rotten secret of good marketing that most consumer products are meant to be sold, not to perform.

Thicker blades have a better emotional allure for many buyers. Thicker means tougher means better in this line of thinking. When I used to work retail in outdoor gear, we would call such designs "easy to sell".
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This says it all about what the OP stated. But i also feel the same way as a consumer. There are many times I grab for my Spyderco millie over my endura or my zt 0562 over my manix 2. I know the thinner blade will hold up just fine but theres a part of my brain that wont compute.
 
noob93 said:
So awhile ago I was In a big knife store fondling many knives and one thing I found was regardless of price point many suffered from poor edge geometry. I would say 90 percent that had poor edge geometry were often times simply too thick to cut well. To my surprise this included many 200-350 dollar knives. Im speaking of production knives here of course. Im not going to start a war and name the specific companies as I know most have many fans on here. I will say though out of all the fixed blades I handled the cheaper bucks and the like had very good edge geometry,compared to others with higher price tags and better steel. Its funny to think that some of those companies using such "superior" steels had big thick grinds. Now I get that many people abuse knives (Iv been guilty on more then one occasion).At some point does it not just become silly to make a knife with such a great steel with poor edge geometry?
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How do you define "poor edge geometry?" and what give you the expertise in the knife making field. I'd like to see the facts not just the gripes.
 
"How do you define "poor edge geometry?"

For me it's pretty simple, if an intended use is for chopping, it needs to be robust enough not to chip or break under heavy loads, but still cut well. If the intended use if for slicing, a heavy blade with a thick edge is wrong.
 
It's a difficult thing for manufacturers to get right it seems. I've seen all sorts of bizarre geometry on a factory edge.

Had a Blur that was at about 8 degrees with an extremely tall bevel on one side and probably 35 degrees on the other. Almost a chisel grind.

Just recently I had a knife the was so obtuse the Wicked Edge guides actually didn't allow enough travel to match it. Spent an hour back-bevelling just to get it to 25dps, which still would've been a bit too thick by my standards.


Perhaps they just err on the side of caution and allow the customer to make modifications to the edge. Except for Microtech of course.
 
noseoil said:
"How do you define "poor edge geometry?"

For me it's pretty simple, if an intended use is for chopping, it needs to be robust enough not to chip or break under heavy loads, but still cut well. If the intended use if for slicing, a heavy blade with a thick edge is wrong.
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Machetes?
 
Most of it has to do with cutting costs (it requires more time/consumables and tighter tolerances to grind super thin behind the edge) and taking advantage of consumers' fears of failure to ensure that the customer doesn't care that the edge is thick. There's economically little to gain by grinding thinner, and the possibility of a lot more consumer complaints, even if it'd be the right thing to do in most cases from a functional standpoint.
 
Every knife has its use, from filet knives to survival knives, and realistic expectations must be had. There has been a trend lately towards heavier, thicker "survival" knives and on that type of knife the public's perception is that thicker and heavier is better, no matter the cost. What the general public doesn't understand is how much difference proper geometry, steel composition, and heat treatment can make to make a job easier, therefore it doesn't sell. Like FortyTwoBlades said, why spend money on something that doesn't help the product move?

FWIW, Buck is known for doing a ton of research on their blade geometry. They use higher end steels on their limited run knives and even their 420HC is no slouch. Very underrated company IMO.

The thing I don't understand at all is these ridiculously thick folding knives that certain companies sell. I love how good locks are getting, and I think strong locks are a great idea, but even the strongest locks will still break before the average blade. They are only hurting their own performance by making the blades so thick they smash rather than slice. In my mind if you need something really strong for chopping and prying, a fixed blade (or the proper tool) is the way to go.
 
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My cheap ass Kershaw Emerson Cqc7k came with one of the best edge geometries on any of my knives. It has had no fragility issues despite being quite keen.

I think the poor geometry is annoying, but what really bothers me are those same 200$ knives with jacked up grinds. My Lionspy has an incredibly obtuse and uneven edge bevel. And even my Lionsteel Sr1a has a wide angle on its tip even though the rest is kosher.
 
noseoil said:
"How do you define "poor edge geometry?"

For me it's pretty simple, if an intended use is for chopping, it needs to be robust enough not to chip or break under heavy loads, but still cut well. If the intended use if for slicing, a heavy blade with a thick edge is wrong.
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It is not that simple...

For chopping wood in the field, what I've found is, if the steel is good quality, a sabre hollow grind blade will tolerate much thinner angles while chopping, while a Full Flat Grind blade will require a thicker more open angle edge.

With a Sabre Hollow Grind, the edge angle can be as low as 12 degrees per side on a 0.020" edge base, and it will tolerate chopping all day long. (Such as a Randall Model 12)

For a Full Flat Grind knife, the edge angle will have to go up to at least 15 degrees per side, preferably sitting on a 0.030" base. Even that is borderline...

(This would not apply to a fully convexed chopper like the SM III Trailmaster or the Fallkniven Thor, because they are not true "Full Flat Grinds". I have found the SM III Trailmaster to be so thickened by the overall convexing that it performed extremely poorly: On these knives, achieving a 15 degree per side final angle is impossible or unlikely anyway, because of their overall "swelled" thickness.)

There are multiple reasons for this particular superiority of Sabre Hollow Grinds, one of the less obvious factors being that wood left on the ground, in the wild, will often "soften" on the outside and "harden" on the inside, creating a medium that will allow more aggressive lateral loads which are more concentrated on the edge itself.

This is because the softer outer will offer less support and allow more accidental twisting movements when unsticking the edge, while the harder inner core will trap the edge more forcefully in a more concentrated manner, often leading to what I call "retrieval chipping": "Retrieval chipping" often has the pattern of two slightly different chips occurring at once close together, this delineating the outer areas of the "pinched" portion: The accidental retrieval "twisting" creates more shear force away from its center axis, hence the "double chipping" away from the center of twisting...

This typically does not happen with Sabre Hollow Grinds blades because, even with thinner edges, the faster increase of cross-section thickness (after it begins, and it of course begins later on hollow grinds than on flat grinds) either pushes the wood apart more forcefully, or naturally "unsticks" the edge better, preventing lateral loads: A hollow grind in effect "naturally" converts lateral loads into vertical "unsticking" motion... A flat grind does not convert lateral forces into vertical motion so well, or it does it less forcefully, so the edge bending just continues without any "unsticking", which sometimes leads to more lateral loads being involuntarily applied...

It is hard to avoid accidental "twisting" in the woods, because the level of "stability" of the wood chopped in the field can vary from thin branches moving around, to very rigid and thicker logs that have softened on the outside. In other words, the retrieval motion is not consistent, and does not have the same effects...

Now Sabre Hollow Grinds are lesser performance "choppers", in absolute terms, compared to Full Flat Grinds, but they get closer if their better protection of sharper edges (by lowering the primary grind line) is factored in: In other words, Full Flat Grinds have to be less sharp for the same durability... Sharper thinner edges mean more versatily in the tasks a chopper can accomplish, so Sabre Hollow Grinds are more versatile, all else being equal...

Another big difference is 10" Sabre Hollow Grind choppers are typically over 20-24 ounces, while Full Flat Grinds are much lighter at around 17-19. This is outweighed in my opinion by the better protection of the edge against lateral loads offered by Sabre Hollow Grinds, especially for emergency shelter building, which is very taxing on a knife...

Gaston
 
GatorFlash1 said:
How do you define "poor edge geometry?" and what give you the expertise in the knife making field. I'd like to see the facts not just the gripes.
Click to expand...

I define poor edge geometry as a grind either too thick or too thin for given application. The facts are right in front of you just go have a look at most "hard use fixed blades" that have a 4 to 6 inch blade for an example. I mean realistically when are you going to use a 4 to 6 inch blade as a dedicated chopper or have to cut your way out of a plain? I know that's not what most people buying those knives are going to use them for except maybe to show off. So why not grind it to a happy medium? That's just an example and I never claimed to be an expert this is simply my opinion as a consumer.
 
To me honestly I would rather have it this way. Speaking more of a thick grind than uneven grinds of course but generally speaking if its thicker I can set it to a degree that I prefer rather than it being a more acute inclusive grind and back tracking.

Either way no company has the perfect answers for everyone's questions and can't please everyone.

Sent from my VS995 using Tapatalk
 
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