Blade Geometry.

[KevinOubre]

I was having a discussion with a friend of mine who uses knives. He isnt a hardcore knife nerd like many of us but he uses them often for work and asks my advice a lot. he recently asked me why I use such thin knives most of the time. He prefers thicker ground knives like the Tuff and the Adamas and plans to buy a Medford :eek: . He was curious about my reasons. I gave him the normal schpeil about higher cutting ability and how the thicker knives don't cut as well. This segwayed us into a discussion about blade geometry as it relates to practical cutting during our normal days. I figured it would make for a nice discussion here. I also did a comparison today between two of my knives, the ZDP-189 Endura 4 and the Benchmade Adamas: http://imgur.com/a/7RBuq" target="_blank . Its as big a difference in geometries as I have in folders.

So, to the point, what are your opinions on blade geometry as it relates to your normal work? How important is thin/thick geometry to your normal cutting? What do you guys prefer? What are your thoughts on it from a practical standpoint, in so far as a blades ability to cut materials you encounter? How do you feel about knives like the Adamas with rather thick grinds and edges vs knives like the Endura which are opposite? Does it really matter that much?

[Cliff Stamp]

One of the things to keep in mind is that you are likely sensitive to such things for two reasons :

-you like knives and use them a lot, even when not strictly required

-you have very different experiences from the different knives you have

I had the same conversation with a friend recently who asked about kitchen knives and commented that cutting ability was all basically the same. I showed them two knives and then did a little work just peeling and dicing up a potato and it was obvious to them then that the difference was there as it was directly comparable. But if you remove the knives from the direct comparison what really would be seen?

If you take two knives for example and dice up a carrot and one takes 2-3 lbs and the other 6-7 then this is a huge difference, it is 2:1. But if you don't have the first knife are you really doing to know the second one is hard or difficult? A normal person can easily exert 10-20 lbs with their hand which for almost any knife will tend to cut almost any ordinary material.

To look at it another way, take some seriously into cars and ask them about something like response to steering. They can likely rattle off a lot of influence and they can drive the same car as you and have a very different perspective for the same two reasons I listed in the above but applied to cars vs knives.

My brother for example has a collection of hammers, to me they are all basically the same but he would see that as saying a Nilakka and the Tuff are both "just knives" and basically just cut things like all of his hammers just basically hit things. It is true in a general sense, but the more you geek out about the specifics the more of the differences you will see.

Of course when you have to do a lot of work -and- you have the experience, then a real practical difference can be seen. I can peel 5-10 potatoes with just about any knife, however when a large family meal is being cooked and I have to peel dozens of them, well I would go get the Herder or similar very nice peeling knife.

[KevinOubre]

We came to the same basic conclusions. Even with the car corollary. He is a big car guy. Discussions with non knife people have really shaped how I view knives. I used to be a bit snobbish I suppose you could say. But they have helped me look at it a lot differently. Also learning how to manipulate edges has helped a lot with how I look at a knifes capabilities. I am much less picky than I used to be.

[tvenuto]

So, to the point, what are your opinions on blade geometry as it relates to your normal work? How important is thin/thick geometry to your normal cutting? What do you guys prefer? What are your thoughts on it from a practical standpoint, in so far as a blades ability to cut materials you encounter? How do you feel about knives like the Adamas with rather thick grinds and edges vs knives like the Endura which are opposite? Does it really matter that much?

Ha, this thread has the potential to rival some of the longer threads here, as I'm sure opinions on this matter are plentiful.

For me, I cut tape, cardboard, zip ties, and plastic packaging. I have actually never attempted to chop with a folder. I live in a city, so god knows if I do somehow encounter some vegetation I'm certainly not going to assail it. In general, I think this makes me prefer FFG knives that are relatively thinly ground. I love my Delicas which I would call a good middle ground as far as that goes. I also love the nice thin Chaparral, which is definitely as thin as I ever feel like I need. The Manix and PM2 are on the thicker side, and it's nice to know you have some extra beef if you're going outdoors or whatever, but for me they could really be thinner with no ill effects. From a practical standpoint? I don't think most people do anything that couldn't be done with a FRN Delica. I think super beefy knives compromise the ability to what they do 99% of the time in favor of what might come 1% of the time, like driving a Jeep Wrangler mostly on the highway (which plenty of people do). So, I see why these knives exist, but it's not my preference.

[bdblue]

In terms of fixed blades, traditionally hunting knives were hollow ground to help with cutting ability. Other types of grinds were done for ease of manufacture or to make the edge thicker for chopping. I think these general characterizations still hold true. Larger traditional folders seem to have hollow ground blades but smaller ones maybe don't have enough blade for that. These days it seems that few modern folders are hollow ground. I think for most uses hollow grinds are fine. They are theoretically weaker in terms of chipping but in reality I don't know how much that matters.

[Ankerson]

Well as most people know thinner tends to cut better as the blade will move through the media easier than a thicker blade will.

Most production folders are ground pretty thin in the .020 to .030 range typically, some are thinner while others are thicker, but most will typically be in that range.

Start comparing a Domino to a Tuff and we have the extremes here so the difference will show up and be pretty apparent depending on what one is cutting.

I doubt most people would really tell the difference in even say .010" difference, while some might depending on what they actually do with their knives on a daily basis so there really isn't a clear cut answer to the question. Would someone tell the difference or would they care? Depends on the individual in the end.

So there aren't any right or wrong answers here, all there is are peoples individual preferences.

For a kitchen knife I would say the thinner the better, for EDC use it can vary more so and likely should depending on the use of the knife.

The geometry needs to match the intended use of the knife in the end.

[KevinOubre]

Well as most people know thinner tends to cut better as the blade will move through the media easier than a thicker blade will.

Most production folders are ground pretty thin in the .020 to .030 range typically, some are thinner while others are thicker, but most will typically be in that range.

Start comparing a Domino to a Tuff and we have the extremes here so the difference will show up and be pretty apparent depending on what one is cutting.

I doubt most people would really tell the difference in even say .010" difference, while some might depending on what they actually do with their knives on a daily basis so there really isn't a clear cut answer to the question. Would someone tell the difference or would they care? Depends on the individual in the end.

So there aren't any right or wrong answers here, all there is are peoples individual preferences.

For a kitchen knife I would say the thinner the better, for EDC use it can vary more so and likely should depending on the use of the knife.

The geometry needs to match the intended use of the knife in the end.

Definitely Jim. Always appreciate your input man :D

[Ankerson]

Well as most people know thinner tends to cut better as the blade will move through the media easier than a thicker blade will.

Most production folders are ground pretty thin in the .020 to .030 range typically, some are thinner while others are thicker, but most will typically be in that range.

Start comparing a Domino to a Tuff and we have the extremes here so the difference will show up and be pretty apparent depending on what one is cutting.

I doubt most people would really tell the difference in even say .010" difference, while some might depending on what they actually do with their knives on a daily basis so there really isn't a clear cut answer to the question. Would someone tell the difference or would they care? Depends on the individual in the end.

So there aren't any right or wrong answers here, all there is are peoples individual preferences.

For a kitchen knife I would say the thinner the better, for EDC use it can vary more so and likely should depending on the use of the knife.

The geometry needs to match the intended use of the knife in the end.

Definitely Jim. Always appreciate your input man :D

Just wanted to cover the broad basics here and since this is the Spyderco Forum stick with that. :cool:

My own testing goes quite a bit deeper into it all and it can get very involved and much more complicated than it would really need to be I think as we seem to be talking about production blades and folders here. So for the sake of not over complicating things just to over complicate them the basics cover it all pretty well and gives the general idea.

[Bill1170]

One thing I'll add to Cliff's excellent first post in this thread is this. As a knife enthusiast, I have paid attention to knives far more than most people do. One result of this is that I am keenly aware (no pun intended) of what a thin blade can handle without damage. It has become second nature to use blades thoughtfully within their capabilities, so I can use thinner geometry with less damage than uncaring knife users can. The habit of cutting mindfully protects my cutlery better than anything else.

[Evil D]

For me it comes down to a few things:

1) What am I cutting? Some things are fine to cut if you just have a thin edge and the blade is thin behind the edge, such as rope. When you start cutting material that's stiff and/or taller/deeper/wider than the height of the blade, like thick cardboard, then the thickness of the blade becomes just as important as the edge for me since the "door stop" effect comes into play.

2) How strong do I really need the knife to be? This is often blown out of proportion due to mall ninja You Tubers driving up hype about strength and whether a knife can be hammered into a car door and not break...when the reality is almost nobody needs an EDC or work knife that can handle that kind of abuse. A good example is the ZT0303 I just got...it's a ridiculous knife to carry for work if your primary use is cutting up boxes, but if you're in an environment where your knife will probably be one of your only tools and will be used for prying/batoning/chopping, then it's perfect. You basically have to choose where you want to compromise... Which is more important, and what do you honestly need for the given task?

3) Last one is simply taste and what I (you) like. This is the ultimate compromise of 1+2. If a person likes their ZT0303 enough to EDC it just to cut up boxes, then who cares? It'll still get the job done, albeit with lower performance. Not everything in this hobby is about absolute maximum performance, otherwise we would be opening boxes with utility blades instead of folders.

The point Cliff was making is basically that ignorance is bliss. If you like it and it works, like his thick blades work for him, then whatever. If someone is interested enough to explore the other end of the spectrum then you take the time to teach, but often you'll end up in the same debate as trying to make someone understand why their $10 flea market knife is inferior to your Spyderco.

[Ankerson]

For me it comes down to a few things:

If someone is interested enough to explore the other end of the spectrum then you take the time to teach, but often you'll end up in the same debate as trying to make someone understand why their $10 flea market knife is inferior to your Spyderco.

When money comes into the conversation things usually go sideways in a real hurry so things are typically less about the knife and more about the money.

There is a lot of garbage out there, much more garbage than quality and it does sell, if it's cheap it will sell is the bottom line there.

So in the end even trying to argue with a lot of them is pointless most of the time if they aren't even in the Buck 110 price range or Spyderco Byrd range before one even starts talking to them.

The really amusing thing is when one starts to think about how much money it costs to manufacture some of these things, figure the retail is $10 to $20, that's retail.. Start figuring in manufacturing costs, overhead, materials, packing and shipping, the markups and we start getting down into the sub $3 range to actually make this garbage in the 1st place. Sometimes it can cost more money to ship the knife from the store to the buyer than it cost to manufacture the thing.

If someone actually thinks they are getting something worth buying then let them fool themselves into thinking that.

[Cliff Stamp]

In terms of fixed blades, traditionally hunting knives were hollow ground to help with cutting ability.

Interestingly enough, I have heard the exact opposite, that hollow grounds were/are used a lot in production simply for ease/cost of manufacturing. However the problem is a lot of this information is second hand and often from biased sources. The people I heard it from for example were strongly promoting their own flat ground knives.

[Cliff Stamp]

... I can use thinner geometry with less damage than uncaring knife users can.

I would note here that kind of perspective can easily wander into fairly nonproductive places. For example here are the edge angles I typically run :

- <0.005":2-4 dps, light use (papers, fruits,vegetables)
- <0.010":6-8 dps, moderate use (plastics,cardboard, clear/hard woods)
- <0.025":10-12 dps, hard use (knotty woods, light metals)

Now does this mean I should regard people who use heavier profiles as being less caring/knowledgeable? That isn't strictly true as in some cases they might simply have different preferences.

I asked a guy on YT who advocated very high edge angles (20-25 dps) for common folding knives and his perspective was that he would rather use a knife with more force in general if it prevented damage in extremes. I have the almost exact opposite preference. I don't mind some damage on occasion if the knife works a bit more efficiently in general. However there is no right/wrong here, it is no different than I generally prefer movies with a science fiction theme than western one.

As a side note, in general it isn't true that thin blades cut better, this is a gross over simplification of how cutting works and it is trivially seen if you take a machete and try to cut through a 2x4. It is obvious almost instantly that it doesn't cut better than a thicker blade because the binding is much heavier on the machete. Mike Swaim in the late 90's on rec.knives talked about how edge angle effected cutting ability. Joe Talmadge and Steve Harvey extended this by noting the edge thickness played a similar role, though not nearly as strong (it is less than linear).

To get a true understand of cutting ability you need to look at the forces on a blade during a cut :

-against the apex
-frictional forces on the flats
-direct forces against the flats

People often confuse the last two thinking they are the same but it should be obvious they are not if you think about it a little. Imagine for example if you try to pound a wedge into a piece of wood. Even if the wedge is mirror polished and even if it is oiled, there is still a lot of force required even though the friction is tiny, this is because you still need to do the work to push the wood apart and that is the third factor.

The reason why cutting ability can actually decrease at some point as you thin out the profile is that all materials have a resilience tolerance which means at some point if they are deflected they no longer return and they stay deformed. When this happens the force they exert against the blade is *much* reduced. This is why cutting blades often are thicker than necessary for strength as they are heavier to ensure that the materials they cut fracture so they don't bind so heavily.

Another factor is that frictional forces can be broken if the knife forces the material to change angle which can break the point of contact. This is why a convex grind can reduce sticking on starchy foods and thus the total cutting force can be less than a thinner blade which allows the food to stay in contact with it over the entire grind height.

--

If you really want to learn about these things in more detail, there is a lot of such research on the performance of blades for cutting wood and machining metals which focuses on how to grind the cutting edges so not only do they make the initial cuts easier, but they cut through the material with minimal force by making the material cut in chips and prevent continuous contact with the blade.

[SpydyLover123]

I defiantly prefer a thin hollow grind for its cutting preformance during everday carry becuse it is more versitile but if I know that i will be doing heavy cuting then i will grab a thicker knife.

[Ankerson]

Basically a balance has to be met between cutting performance, edge retention, toughness/Ductility, strength, stain resistance, RC hardness and geometry.

A lot goes into the process before a steel is even chosen for the model, including the intended use range for the model.

I will go back to the TUFF vs Domino example:

The TUFF is made to be a harder use knife, something that could possibly be used as a hunting blade for some that like to use their knives harder to pop out hip joints or split the rib cage. While being a folder the blade geometry and the steel could handle that type of use. Although a fixed blade or a saw would be better in general, preferably a bone saw I would think.

The Domino on the other hand is more of a slicer with it's thin geometry so it would make for a nice skinning blade or some butchering if needed for those who like to use folders for that task and the steel will hold an edge for along time. Would prefer a longer blade for those tasks, but you get the idea, it's a lighter use knife.

Either knife could be used for EDC and I am sure they are and both are perfectly capable of performing basic EDC tasks in general as in cutting stuff. One will cut stuff a little easier than the other one in general while the other could be used for harder tasks due to the thicker geometry.

Comes down to needs and wants in the end and throw in likes and dislikes for good measure. :D

A simple photo example, both knives are M390, one is 3/16" thick spine and .035" behind the edge while the other is .120" and .006" behind the edge.

I would hope people could tell what knife is going to cut better and what would be better for harder use.

Like I said in my other post, it's very basic stuff here, it's not complicated at all.

[elena86]

A high hollow grind as in Sebenza 25 covers all the bases IMO.It's a great combo between a flat grind and a hollow one.The same in Benchmade Ritter Griptilian.I'd like to see that kind of grind in a new Endura/Delica generation.

[Evil D]

Like I said in my other post, it's very basic stuff here, it's not complicated at all.

WRONG! I need graphs and pie charts and statistics and analogies and comparisons! I need blind tests conducted by cutting thousands of feet of randomly selected cardboard, I need blindfolds and unmarked blades ground exactly the same by a machine! I can't wrap my mind around all this simplicity and common sense!

[tvenuto]

Like I said in my other post, it's very basic stuff here, it's not complicated at all.

WRONG! I need graphs and pie charts and statistics and analogies and comparisons! I need blind tests conducted by cutting thousands of feet of randomly selected cardboard, I need blindfolds and unmarked blades ground exactly the same by a machine! I can't wrap my mind around all this simplicity and common sense!

Of course, but all that was never the question. The OP wasn't wondering how you tell which knife will cut better, or asking for proof that a thinner knife would cut better, or whether a thicker knife would be better for hard use. The OP is asking for your thoughts and opinions on how important cutting ability is to you. I'm sure there's people here who would prefer their PM2 was thinner, and people who prefer it was thicker. I'm sure some here carry a tuff even though they know it's sub-optimal for 95% of their cutting tasks, and there are others that went so far as to have their southard ground down aftermarket to improve it's cutting ability. I think the differing preferences for hollow v FFG have been interesting.

So, to the point, what are your opinions on blade geometry as it relates to your normal work? How important is thin/thick geometry to your normal cutting? What do you guys prefer? What are your thoughts on it from a practical standpoint, in so far as a blades ability to cut materials you encounter? How do you feel about knives like the Adamas with rather thick grinds and edges vs knives like the Endura which are opposite? Does it really matter that much?

[Evil D]

Some days my sarcasm is totally wasted lol.

I don't think we can ask for opinions on what we prefer without going into why..

[Donut]

I had trouble cutting some cardboard with my Yojimbo 2. The blade is thick and it was actually ripping the cardboard apart before the edge could get to it.

Fortunately, it is hollow ground and the spine goes towards the edge near the tip, so I could cut at an angle near the tip and avoid the problem.

I should probably try to get pictures of problems like this.