Temporal Edge Retention

[Manifestgtr]

CPM Cruwear exhibiting extreme temporal retention of front end sharpness:

Found a hair on my jacket this afternoon and figured “might as well”. After two months the PM2 is almost exactly as sharp as I left it in early January. I remember sharpening it right around the new year and thinking “2023 is off to a good start”.

Truth be told, I don’t remember the stropping grit but it was probably 2k since that’s where I like to keep my cruwear. I’m also not particularly difficult on this knife. If I have a lot of work to do, I grab an endura or a stretch…so this isn’t a comment on cruwear’s slicing edge retention. Just an observation on how well it’s kept its extreme front end sharpness over the course of two months.

[ikaretababy]

The exact mechanism of why it moves is not known. However there are some clues that could be in understanding more about the elastic/plastic transition of knife steels on a microscopic scale since bulk properties of a material can be different than on a microscopic scale.

could it be the metal expanding or contracting teeny tiny amounts because of ambient temperature changes and thats enough to alter the orientation of the very small amount of steel in a small burr?

[Bemo]

It's all about quantum entanglement.

[RustyIron]

Any results I get are from a sample size of precisely one. That doesn’t escape me…I know that science thrives on repeatability and objectivity above all else.

Nonsense! Real science is based on Tik Tok Videos, who gets the most likes, and who talks the loudest.


Your experiment inspired me to give it a shot. So now we'll have a sample size of two guys using different methodology in wildly uncontrolled environments. But as long as we're having fun, it will be a worthy endeavor.

I sharpened up a Manix 2 Maxamet and chopped up some filament on my super-technological homemade sharpness tester. The measurements are scribbled down, the knife put away, and my calendar marked for March 27.

If I was a betting man, it would be that the readings are going to be similar in a month.
Time will tell...

IMG_0148 copy.jpeg (53.67 KiB) Viewed 777 times

[RustyIron]

It's been exactly thirty days, so I whipped out my trusty Manix 2 LW Maxamet and put it to work cutting filament. Thirty days ago I marked the blade and scribbled down 112 grams. Today I repeated the test as similarly as possible, and the average pressure to cut the filament was 114 grams. From this sample of one, I'm going to go out on a limb and claim unequivocally that blades do not spontaneously dull themselves while sitting unused in my desk drawer.

[ladybug93]

It's been exactly thirty days, so I whipped out my trusty Manix 2 LW Maxamet and put it to work cutting filament. Thirty days ago I marked the blade and scribbled down 112 grams. Today I repeated the test as similarly as possible, and the average pressure to cut the filament was 114 grams. From this sample of one, I'm going to go out on a limb and claim unequivocally that blades do not spontaneously dull themselves while sitting unused in my desk drawer.

i know this isn't spyderco related, but i'd be curious to see a similar test with something like 1095. i've had that go dull on me while in my closet, i'm pretty sure.

[sal]

I don't think it's quantum entanglement or Tik Tok. It's Astrology; Your knife will go dull when Mars is in Uranus.

sal

[dan31]

good one Sal!

[prndltech]

Im pretty sure it’s the same gnomes that steal your socks in the dryer

[RustyIron]

I don't think it's quantum entanglement or Tik Tok. It's Astrology; Your knife will go dull when Mars is in Uranus.

Kristi! Kristi!
See what he did there?

[Kevinim82]

I don't think it's quantum entanglement or Tik Tok. It's Astrology; Your knife will go dull when Mars is in Uranus.

Kristi! Kristi!
See what he did there?

Hahahahahahhaha!!!!

Sal has a good point! It’s hard to see though, you see, Uranus is not visible to the unaided eye.

[Kevinim82]

This image is for reference to Sal’s comment.

[Bill1170]

Astrology aside, maybe repeat the test on some stainless steel blades? I recall the theory being posited that some stainless steels “relax” over time from a keen apex to a more rounded one. My sense was that this was observed as a 440A/440B problem.

[sal]

I hear some interesting arguments for Chromium being the culprit due to Chrome Oxide.

sal

[u.w.]

I hear some interesting arguments for Chromium being the culprit due to Chrome Oxide.

sal

LOL again! and if not chrome (oxide) lol... perhaps Klingons in the vicinity of Uranus ...

u.w.

[Bolster]

I hear some interesting arguments for Chromium being the culprit due to Chrome Oxide.

sal

LOL again! and if not chrome (oxide) lol... perhaps Klingons in the vicinity of Uranus ...

u.w.

Wait a sec, I can't tell if this is a joke or not. Chromium does produce an oxide, being "readily oxidized by the atmosphere." It looks like there are actually several types of chromium oxides. I'm not a chemist, but if there are ferric oxides (ie, rust) that dulls, why wouldn't chromium oxides also dull?

[Bolster]

IMG_0148 copy.jpeg

I like your tester! I want to make one like it! Question: How do you get the filament stretched across at the same tightness each time? I assume that matters but I could be argued out of that notion.

[DunninLA]

Here is my hypothesis. I don't believe it possible for the shape of an apex to change sitting idly over time.

1. you sharpened the chaparral very well, either by luck, or b/c XHP is easy to sharpen and propely debur.
2. on another knife, you left a small burr, but the burr was straight so the knife cut like it was sharp, and you cut with that knife a couple of times... which caused the burr to move to one side, thus dulling the knife, but you didn't notice it.
3. You pull out the knife from #2 a couple of months later, and notice it isn't as sharp as when you first sharpened it. But you forgot you used the knife a couple of times and weren't paying attention to its sharpness. That is, that knife was dull when you put it away for two months.

[JD Spydo]

I could be nuts, but I always felt my S30V Manix is like this. I will sharpen it, let it sit for awhile, few weeks, then it just does not have the same bite.

I use to experience that with my older Benchmade Boguszewski Spike model ( ATS-34 blade steel). It seemed like it always got dull quickly and I was always extremely careful with it. For whatever reason I found myself spending a lot of time maintaining it's edge and it always seemed to get dull very easily. The ATS-34 blade on most Benchmade models were not nearly as well heat treated as the ATS-34 Spyderco blades were>> it sure seemed that way. And just to think at one time ATS-34 was considered a "supersteel" among knife enthusiasts.

[RustyIron]

I like your tester! I want to make one like it! Question: How do you get the filament stretched across at the same tightness each time? I assume that matters but I could be argued out of that notion.

Thanks. It's just a chunk of round aluminum into which I carved some slots and added a couple screws. It's silly and pointless, but sometimes I just like to measure things. It makes me feel better to be able to put a number to my sharpening. Without numeric data, evaluating sharpness is just someone's subjective impressions.

Good question on the filament tension. My ultra-precise tensioner is my fingers. I pull it taught, tighten the screw, and call it good. If I do a bunch of identical tests, the variation of my readings is about 5%. Part of that variation is surely filament tension. But there are so many other potential sources of inaccuracy that it doesn't really matter. I'm happy with 5%.

I copied my contraption from pictures of a commercial product. I don't know what kind of accuracy is attainable with that one. I expect that it will be similar to mine.