Edge Angle vs Thickness BTE

tomhosang said:
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.
Click to expand...
It was important for Steve to show that the behind the edge thickness doesn't make the apex cut longer, the apex is the apex, in the real world they are intertwined.

The title of this thread is misleading. One needs both in reality and some tasks will put more emphasis on one vs the other.

Variables like these are important to understand so that we can all be on the same page and excited when we see something extraordinary rather than it just being a mysterious variable that is hiding in the shadows.
 
DeadboxHero said:
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.
Click to expand...


Great post, Dead:

But it gets even more complicated. Heat treat + geometry + steel have to be matched to the range of tasks, which I know you know.

Heat treat can be pushed in a lot of different directions, some work great with some tasks, some don't.

Same with geometry. Same with steel.

One of the reasons that Fredrik Haakonsen likes to use A8(mod), a super tough but not exceptional wear-resistant steel, is that the toughness protects the edge from microchipping that can wipe out cutting performance. So in many cases, depending on the task, an ordinary-wear steel can outperform a high-wear steel. As mentioned above, edge stability is important.

Toughness is a property often overlooked in knife steels, often on behalf of corrosion and wear resistance. The thing is that a sharp edge with a decent edge angle (<35° total angle) needs toughness to avoid breakage of the edge/chipping, especially when working with hard materials like wood. Because of this, edge retention of this steel will be better than higher alloyed steels and even powder steels for many purposes.
http://xxxknives.blogspot.com/search/label/Steel: A8-mod
​
The number of variables and the complexity of each variable, not to mention near infinite combinations of variables, makes knives extremely resistant to common wisdom.
 
@Larrin did a cool article on
knifesteelnerds.com

"Sharpeness vs Cutting Ability"


Sharpness being apex radius

And cutting ability being "edge width" or behind the edge thickness BTE

rIKA8uB.png

In the graph, you can see different materials being cut. These are both thin BTE knives

The black line is the sharp knife
The grey line is the dull apex knife.

Y-axis is force needed to cut

X-axis is depth of cut.

So in the first picture you can see that in the soft pumpkin flesh, the dull knife and the sharp knife showed no difference.(the grey and black lines match)

This is facinating to see this phenomenon measured.

You can also see that with cutting a slice of smoked ham that the dull knife really showed the force needed to cut climbing exponentially and that the apex radius was more significant than purely bte.


I strongly urge folks to read the article.
Can be found here
https://knifesteelnerds.com/2018/08/06/sharpness-vs-cutting-ability/

The source for the test in this graph used above and from knifesteelnerds is cited and sourced from here.
https://www.tib.eu/en/search/id/elsevier:doi~10.1016%2Fj.jfoodeng.2016.04.022/Analysis-of-the-sharpness-of-blades-for-food-cutting/
 
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DeadboxHero said:
Heat treatment, geometry and steel.
Click to expand...

Can I get an amen?!


DeadboxHero said:
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.
Click to expand...

Preach brother. Preach!

:thumbsup:
 
In my own experience, and I believe cliff stamp has found this as well... In terms of cutting ability it ranks in this order:
  1. Edge angle
  2. Bte thickness
  3. Blade stock thickness
(I'm sure grind type falls in there as well)

So for the most powerful increase in cutting performance you need to decrease edge angle.
 
Isn't BTE thickness only a sum of edge angle, grind, and blade stock thickness, and changing any of the three will change BTE thickness result?
 
This is why we have super steels.100 yrs ago the best steels were fairly easy to sharpen and folks were able to easily maintain those blades.That's why so many old knives were sharpened to tooth pick status,they were actual esers. I wonder what some historian in the future will think of all the great condition knives they come across?Most old knives were ALOT thinner stock to begin with than we have today.To get the tough blades they went thicker and sacrificed cutting performance.A thicker blade equals more friction more force to cut thin are less force.ymmv
 
Baron Mind said:
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.
Click to expand...

0) move past the random pondering stage :)
0) define ... performance ... maybe even measure some things
0) draw pictures, a wedge, a triangle, is defined by three sides, or two angles and a thickness


imgur.com/a/2Cl3Ga2

...
15dps25thou-10dps30thou.png

20dps20thou-15dps25thou.png




Which triangle is more pointy?
Which triangle fits inside which triangle?
What is performance?
How does it compare to the ... competition ... $1 knife? $6 knife?...



See also whats-the-lowest-functionable-angle-by-steel-type.1587190/#post-18129004

Define the hardest task the knife has to perform,
Then perform said task (cut stuff)
If edge gets deformed, increase angle
If edge not deformed, lower angle
Repeat
Repeat
Repeat

With calipers you can simply check against the list of ranges of thicknesses/angles for various cutting tasks/steels in whats-the-lowest-functionable-angle-by-steel-type.1587190/#post-18129004
 
Here is a neat video that can add more to the discussion.

CPM 15V at the limits of geometry and Hardness.

You can see how the BTE effects this

Cutting ability and durability are an inverse relationship.

Here you can see what extreme cutting performance looks like



Here is when it's abused and also showing what geometry is the limit to not take damage but still be thin.

 
bucketstove said:
0) move past the random pondering stage :)
0) define ... performance ... maybe even measure some things
0) draw pictures, a wedge, a triangle, is defined by three sides, or two angles and a thickness


imgur.com/a/2Cl3Ga2

...
15dps25thou-10dps30thou.png

20dps20thou-15dps25thou.png




Which triangle is more pointy?
Which triangle fits inside which triangle?
What is performance?
How does it compare to the ... competition ... $1 knife? $6 knife?...



See also whats-the-lowest-functionable-angle-by-steel-type.1587190/#post-18129004

Define the hardest task the knife has to perform,
Then perform said task (cut stuff)
If edge gets deformed, increase angle
If edge not deformed, lower angle
Repeat
Repeat
Repeat

With calipers you can simply check against the list of ranges of thicknesses/angles for various cutting tasks/steels in whats-the-lowest-functionable-angle-by-steel-type.1587190/#post-18129004
Click to expand...

Just saw this reply, very cool, thank you.
 
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