DPS 18 versus 20 Degrees

R

Rojo

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Apr 21, 2013
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I am a newbie to the CPK world.

Curious to know if anyone has noticed a performance difference between older FK2 knives with a stated DPS of 18 degrees and the newer field (and other knives) with a DPS of 20 degrees.

And, if you did notice a difference, what was it? Do you have a preference?

Thank you.
 
I know a bit about sharpening.


And you know, it still all depends on the overall thickness of the cutting edge. By itself, a value like 18 DPS or 20 DPS doesn’t mean much in a vacuum.


But if we take something like an FK for example, the difference between 18 and 20 is this: when you keep resharpening at 20 DPS (say, 4–5 times a year), you save steel and the blade as a whole — you remove less material each time.


18 DPS gives you better initial sharpness, and overall it stays sharper longer, especially when your edge is already getting dull and you’re about to resharpen it. Because the geometry at 18 DPS is naturally thinner.


So it all depends on your tasks, dude.


If you only cut soft materials or meat, you can even go below 18 if you want.


For example, at 20 DPS with CPK knife geometry — which is already thinner than most — your knife ends up noticeably thinner than others even at 20, and you can really feel it during use.


18 DPS makes a real difference if you’re cutting a ton of meat. The other day I sliced up around 30 kg of meat into small pieces, and my DEK3 is currently sharpened at 16 degrees. It’s literally a razor.


So honestly, the difference between 20 and 18 isn’t that big in terms of pure sharpness and performance.


But the amount of material (steel and blade) you save over real, long-term use is huge. Sharpen the knife 100 times, and those two degrees make a massive difference.


In short: if the knife is just a pocket carry and you’re cutting cardboard, wood, thick rubber hoses, or reinforced hoses like I do, then just go with 20 DPS per side and don’t overthink it.
 
We do our heat treat development work at 18 DPS because the stuff we do doesn't really show a lot of damage at 20.

There is a significant and meaningful difference in edge durability between 18 and 20.

A lot of people think they're sharpening at 20 because they use a 20° wedge as a reference but if that wedge is relative to the opposite bevel and that bevel is 5°, they're actually sharpening at 25°

We sharpen at 20° relative to the center plane of the blade. This is where the average American runs their kitchen knives. And it's where a lot of people who think they're sharpening at 15 degrees per side are actually running their knives. It's a good general purpose angle.

It's thin enough.

If you go down to 18 you will get better cutting performance but at the expense of developing edge damage in rough use that you won't see at 20

While you can run it down to 15, a steel like 4V at HRC 64 does better at that narrower geometry.
 
A difference of only a couple degrees makes a significant difference in the behavior and longevity of the edge.

Anybody comparing knives or heat treat that are not controlling their edge angle exactly are looking at a poor signal to noise ratio.
 
This is my DEK3.


The day before yesterday I cut about 20 kilograms of extremely tough meat with it.


A ton of vegetables and other stuff too.


Then I used it to light a campfire.


And I cleaned the meat that was stuck to the skewer right with the cutting edge.


At 16.5 DPS.


I didn’t even get any noticeable damage.


Did it get dull? Of course.


I literally use it, most likely, harder than I should.


Especially since I resharpened it to my own preferred angle.


What changed at 20°?


Most likely, because of my sometimes stupid usage, it wouldn’t have dulled at all and would still be razor sharp.


A lower angle at least makes you think a little before scraping stuck meat off a piece of metal with the edge 😅


On the other hand, a thinner edge is much easier and faster to strop on leather (less DPS).


A thicker edge is a bit harder to align properly on leather (more DPS).


The HDFK that I sharpened at 22 DPS seems to live forever on leather, because there’s so much metal behind the cutting edge. Delta 3V is an extremely interesting steel for everyday — and sometimes dumb — use.


For example, I cut pipes that literally have metal inside using the SDFK or HDFK.
 

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Damn, I also perceive “sharp” a bit differently.


Basically, for me, “the knife became dull” means it can no longer, for example, shave hair.


Or cut paper perfectly clean.


I keep sharpening my DEK3 to a lower and lower angle simply because I’m curious how thin and how long-lasting the edge on Delta 3V can stay in real-world use — so it forgives my stupidity.


For example, I can be whittling wood for kindling and accidentally smack the cutting edge into a metal grill.


😅
 
Nathan the Machinist said:
We are the current world and national blade sports champions because we have this stuff dialed into a science
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This is a very very true statement , I've had a chance to use a CPK blade sports knife a couple times , they are scary sharp!!!!!!!!!!!!

The thing that is even more impressive is the speed and the process Nathan sharpens with
 
Nathan the Machinist said:
We are the current world and national blade sports champions because we have this stuff dialed into a science
Click to expand...
Do two different organizations run World / National competitions or does the former also include some Intl. participants? Maybe someone from Canada or Canadian heritage rep'ing Canada? Just want to know if this sport is spreading beyond the borders here in North America which also includes MX.

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Casinostocks said:
Do two different organizations run World / National competitions or does the former also include some Intl. participants? Maybe someone from Canada or Canadian heritage rep'ing Canada? Just want to know if this sport is spreading beyond the borders here in North America which also includes MX.

View attachment 3192630
Click to expand...

There are, and has been, other participants but they come to America and get spanked and don't want to continue to participate so right now it's pretty much all Americans
 
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