Edge Angle vs Thickness BTE

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Baron Mind

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So we know two things that increase cutting performance are lower edge angles and lower BTE measurements.

These properties are inversely related however. One must assume that the benefit from lowering the edge angle outweighs the resulting thickening of the BTE measurement, but has this been proven to be true, and if so, is there a point where that is no longer true? I.e going from 40 inclusive and 20 thousandths bte to 30 inclusive and 25 thousandths BTE results in greater cutting performance, but going from 30/25 to 20/30 isn't?

Just a random pondering of an edge junkie. Any idea? Theoretical, mathematical, or empirical contributions are all welcome.
 
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I'm not sure I fully understand.
Are you saying that when you go shallower sharpening angle that the behind the edge thickness increases automatically?

My thoughts :
forget 20 thou or more behind the edge go for like 10 or even less ! ! ! !

40 inclusive ! ? ! ?
My God man . . . we aren't talking about axes here . . . anything over 30 is . . . is . . . madness :eek:
:)
 
and another thing . . . go here LINK > > > and page down to the last three of my photos.
The Pendleton Hunter in 3V is like 10 thou behind the edge at less than 30° inclusive. I hit a big old steel staple with it while cutting up a double wall corrugated shipping crate and it left a V notch in the staple and you could see nothing on the blade edge.
Good enough for me :thumbsup:
 
Eventually you get to full flat ground zero edge...my favorite;)

~Chip
 
Those extremely wide angles and thick behind the edge is how makers of cheep knives with inferior heat treats try to keep their edges from failing.

On the other hand check out what is possible with a little TLC.
 
jpm2 said:
.080” bte
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o_O
:confused:
I'm doing "the dog look".

Do you mean .008" bte ?
you sure don't see anything near the top of the Ankerson test with .080" bte.

Note what happened when the Stock Manix at .030" bte was taken down to .005" bte ! ! ! !

S110V - 1120 - Manix 2 - 62 RC - Regrind to .005" behind the edge.
CPM 10V - 1100 - Spyderco/Farid K2 - 63 HRC - .020" behind the edge.
CPM S110V - 1080 - Spyderco Military - 63-64 RC - .020" Behind the edge
. . .
. . .
CPM 4V - 740 - Big Chris Custom - 63 RC - .008" - .010" Behind the edge.
CPM M4 - 740 - Phil Wilson Custom - 65 RC - .015" Behind the edge.
S110V - 720 - Manix 2 - 62 RC - .030" behind the edge
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In my view . . . for a smallish folding knife like the Manix . . . .030" bte is a REJECT.
.080" bte is specs for a cold chisel.
 
I think what has to be factored in is edge stability. A lower bevel angle is not, in and of itself, the path to better cutting performance. It is, as you suggest, a combination. Steel type also has to be factored in. The magic happens when all three of those things come together to amazing cutting performance yet retain an edge that doesn't roll or chip with a stern look.

Reverend DeadboxHero DeadboxHero from the Church of High Steel seems to be finding 15dps is a pretty ideal balance. Then it's what BTE can the steel support?


 
If you have a knife made to your specs or if you have a blade reground to your specs, you can get whatever edge width and edge angle that you want.

However, as you sharpen and resharpen the knife, the edge width is going to get wider, except in certain cases for a hollow ground knife. (Which is a good reason to go with high-wear steels so less metal is removed to keep it sharp.)

If you just lower the angle by reprofiling, you're going to widen the edge. The effect will be reduced in thin blades and exacerbated in thick blades, which is another reason why thin blades cut better over the life of the knife.

If I remember correctly, Larrin found that edge angle is more important than edge width, although my own sense is that edge width is more important.

Also, how sharp the edge is (how narrow the apex), the better it will cut.

My favorite combo is 15 dps for the angle and 0.015 inches for the width.
 
^^^Bottom line, like he says, you're essentially trying to push a wedge through the material. You have to take all the factors into consideration.
 
BTE measurement does not affect your edge retention (depending on what you're cutting). It only makes it easier to cut. Edge angle does change edge retention, however. My buddy Steve illustrated this well.

 
Videos are nice, but to throw up a 37 minute video without summarizing the key points and evidence is not very helpful. Rather than discussing the issue, you're just assigning homework.

Ankerson's tests showed that edge width does play a major role in edge retention -- or at least in increasing the number of cuts on rope that can be achieved up to a certain blade pressure.
 
Twindog said:
Videos are nice, but to throw up a 37 minute video without summarizing the key points and evidence is not very helpful. Rather than discussing the issue, you're just assigning homework.

Ankerson's tests showed that edge width does play a major role in edge retention -- or at least in increasing the number of cuts on rope that can be achieved up to a certain blade pressure.
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Fair enough. I just posted the video for anyone who wanted to watch. Here's the summarization:

He tested 2 Manly Wasps in 12c27. One being 0.016" BTE and the other being 0.008" BTE. So, the exact same knife, in the exact same steel, from the exact same maker. The only difference being the BTE thickness. His test media is cardboard, which is something many of us encounter on a daily basis (way more than rope). This is why I said it depends on what you're cutting. The cardboard does not bind up on the knife like something like rubber would do. For this reason, BTE doesn't matter as much. Steve got very similar results between the two Wasps. The 0.006" cutting 14 feet more than the 0.016" one. This may seem like a lot, but is only an 8% difference. Almost negligible. It is not a black and white subject. Any difference in BTE thickness is negated by the edge angle, the edge finish, and the media being cut. It will or won't make a difference based on those factors.

Also, Ankerson's tests are a tremendous resource. It gives us a great baseline to go off of. The same thing goes for any of the YouTube testers including Steve or myself. All of this is to give people a reference point for certain steels. Depending on the knife, company, use, etc; anyone's experiences may vary.
 
tomhosang said:
Fair enough. I just posted the video for anyone who wanted to watch. Here's the summarization:

He tested 2 Manly Wasps in 12c27. One being 0.016" BTE and the other being 0.008" BTE. So, the exact same knife, in the exact same steel, from the exact same maker. The only difference being the BTE thickness. His test media is cardboard, which is something many of us encounter on a daily basis (way more than rope). This is why I said it depends on what you're cutting. The cardboard does not bind up on the knife like something like rubber would do. For this reason, BTE doesn't matter as much. Steve got very similar results between the two Wasps. The 0.006" cutting 14 feet more than the 0.016" one. This may seem like a lot, but is only an 8% difference. Almost negligible. It is not a black and white subject. Any difference in BTE thickness is negated by the edge angle, the edge finish, and the media being cut. It will or won't make a difference based on those factors.

Also, Ankerson's tests are a tremendous resource. It gives us a great baseline to go off of. The same thing goes for any of the YouTube testers including Steve or myself. All of this is to give people a reference point for certain steels. Depending on the knife, company, use, etc; anyone's experiences may vary.
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Thank you for taking the time to explain the video. Much appreciated.

I'd agree that there are a lot of variables that come into play.

Intuitively, I'd think that cutting rope would be less sensitive to edge width because the fibers spay quickly, getting out of the way of the rest of the blade. But I don't really know.

Both those edges in your test were pretty thin, with the 6 thousandths being near the extreme. I have a Rex 121 knife with that edge geometry made by Bluntcut. I use it to cut cardboard exclusively. It never gets dull, but then the steel is far more wear resistant than 12c27. That thin edge may be suffering from poor edge stability (resistance to chipping and blunting).

The real problem with cutting cardboard, from my experience, is the thickness of the blade. Thicker blades, especially if the cardboard is thick and stiff, are impossible, while my thin (0.078 inches at the base of the spine and 0.0260 inches a quarter inch back from the tip) Bluntcut knife just glides through it.

This is always the trouble with knives. Nothing is simple. I think you're right that we have to take into account a lot of variables, although that makes conclusions read like the fine print that comes with my credit card.
 
People do
tomhosang said:
Fair enough. I just posted the video for anyone who wanted to watch. Here's the summarization:

He tested 2 Manly Wasps in 12c27. One being 0.016" BTE and the other being 0.008" BTE. So, the exact same knife, in the exact same steel, from the exact same maker. The only difference being the BTE thickness. His test media is cardboard, which is something many of us encounter on a daily basis (way more than rope). This is why I said it depends on what you're cutting. The cardboard does not bind up on the knife like something like rubber would do. For this reason, BTE doesn't matter as much. Steve got very similar results between the two Wasps. The 0.006" cutting 14 feet more than the 0.016" one. This may seem like a lot, but is only an 8% difference. Almost negligible. It is not a black and white subject. Any difference in BTE thickness is negated by the edge angle, the edge finish, and the media being cut. It will or won't make a difference based on those factors.

Also, Ankerson's tests are a tremendous resource. It gives us a great baseline to go off of. The same thing goes for any of the YouTube testers including Steve or myself. All of this is to give people a reference point for certain steels. Depending on the knife, company, use, etc; anyone's experiences may vary.
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Nah
BTE does matter for EDC, ESPECIALLY cardboard. You're taking the test too literally.

Steve was just showing that it didn't effect the Apex longevity. (That has to do with apex radius/angle)
if he kept cutting the cardboard for raw endurance, the thinner bte would cut better than the thicker one due to less resistance

So, in an endurance test just cutting cardboard until unable, the thinner BTE wins.

This phenomenon is important for understanding why some folks knives are still cutting despite not being very sharp.(Opinel for example)

The reason why thin BTE is important is because the end user can always play with lower angles when they get the knife. But it takes great time and skill to take a thicker Grind to a thinner bte.
 
This is why when you combine thin BTE with lower edge angles and a steel that has the chemistry to support high hardness and a heat treatment to bring out the best microstructures you win at cutting performance.

Connect the dots guys.
No one thing stands alone.

However think about this.

Heat treatment, geometry and steel.

Let's say you can only choose one and the other two are mediocre, not bad, but not great.

Now for me I'd cheat and pick heat treatment and Grind it thinner LMAO.


But for the common man, picking great geometry would be the winner in cutting performance.
What is the use of great steel and great heat treatment without the geometry to express it?

This is why I started making knives, I was tired of begging and having to pick and choose. Why not have it all? Sure it costs a lot but its nice to have options and life is short.
 
DeadboxHero said:
People do


Nah
BTE does matter for EDC, ESPECIALLY cardboard. You're taking the test too literally.

Steve was just showing that it didn't effect the Apex longevity. (That has to do with apex radius/angle)
if he kept cutting the cardboard for raw endurance, the thinner bte would cut better than the thicker one due to less resistance

So, in an endurance test just cutting cardboard until unable, the thinner BTE wins.

This phenomenon is important for understanding why some folks knives are still cutting despite not being very sharp.(Opinel for example)

The reason why thin BTE is important is because the end user can always play with lower angles when they get the knife. But it takes great time and skill to take a thicker Grind to a thinner bte.
Click to expand...

I do agree there, Shawn. Going until it won't cut cardboard any longer, the thinner one would win no question. I guess I was just thinking of Steve's results and not the bigger picture.
 
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