K390 edge holding experience

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michaelm466
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K390 edge holding experience

Postby michaelm466 » Mon Mar 24, 2014 12:14 am

I work at a clothing store where we have to cut up (make damaged/returned/washed and worn clothes unwearable and unreturnable if some one took them out of the dumpster) clothes. Today I was tasked with "damaging out" 621 items (we have to scan each barcode before destroying it).

I did a similar test using a Benchmade Vex in 8cr14mov (35 no longer shaving, @ 70 lost its working edge) and a Saber Grind Spyderco Delica in ZDP-189 (105 before no longer shaving and stopped at 200 with still a working edge).

The items to be destroyed consisted of (roughly) 40% leather, canvas or faux leather shoes (a significantly higher level of shoes compared to the ZDP-189/8Cr14 test), 15% denim and 45% polyester or cotton shirts.

This time a Spyderco Endura FFG in Superblue steel was used as well as K390 Mule Team. I started with the Endura first and made it through about 150 items however switched because I could feel the FRN handles flexing when being forced through some of the thicker shoes, at 150, the Super blue was just barely shaving. The K390 Mule then took over from 151-621 the mule was the only knife used, it started easily shaving sharp at around the at around the 450 mark (300 items in for the mule) there was no noticeable difference in sharpness from the 151 item mark, at around the 575 mark, the edge was finally have problems shaving, but could still scrap shave, there was also a slightly noticeable difference in the front/mid blade compared to the back of the blade which hadn't gotten as much use and was still as sharp as it was in the beginning. When I finished all 621 items (8 hours, and 2 small blisters later) the Mule was just barely able to scrap shave still, and still had a very useable working edge. I did notice that a few extra pounds of force was needed to cut through the thicker leather items, but it was so difficult I would have switched if I had a different knife available like I had to with the BM Vex. Needless to say I am VERY impressed with the K390's edge holding as well as surprised that it took about 5 minutes on the sharpmaker to bring back to its initial sharpness (no diamond stones used). I'll do a quick summary, though I'm not sure it means much because these blades all have different profiles and the latter two definitely had a more difficult group of media to get through.

Steel------lost shaving edge----lost working edge
8cr13mov--35 cuts---------------70 cuts
ZDP-189---105 cuts--------------200+
SuperBlue---150---------------N/A
K390--------600-----------------N/A

I'm definitely looking forward to/hoping for more K390 and the like (10V) from Spyderco in the future.
Also the Superblue is amazing to sharpen 7 passes on each set of stones (white and brown) brought it up to a screaming sharp edge.

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Postby Zenith » Mon Mar 24, 2014 12:38 am

Thank you for sharing your findings.

What grit finish did you put on the edge and at what angle?
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Postby michaelm466 » Mon Mar 24, 2014 12:43 am

Zenith wrote:Thank you for sharing your findings.

What grit finish did you put on the edge and at what angle?
Brown stones to white stones and finished with a few swipes on loaded leather strop at 30 deg.

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Brock O Lee
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Postby Brock O Lee » Mon Mar 24, 2014 3:25 am

Thanks, that's very interesting...

Do you cut on some kind of cutting board/surface?

Have you ever used S90V/M390/M4 etc for this task?
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Postby xceptnl » Mon Mar 24, 2014 6:55 am

Brock O Lee wrote:Do you cut on some kind of cutting board/surface?

Have you ever used S90V/M390/M4 etc for this task?
I would like to know more about these questions as well.
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Postby Cliff Stamp » Mon Mar 24, 2014 7:08 am

I would be curious to know what kind of consistency you could generate if you repeated that a few times - giving your hands some times to rest.

Interesting that the SB was comparable to the ZDP-189.

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Postby nccole » Mon Mar 24, 2014 8:10 am

Thanks, I appreciate the real world testing. The more scientific testing is great, but sometimes just some real world experience is what I want to know. I won't be using a scale, and all the controlled methods that the more scientific uses. You might be twisting every now and then, you might smack something unintentional, and these real world variables although hard to control naturally are nice to see. I think I dull my knives more from micro edge deformation than pure wear resistance. I am not too surprised about Super Blue holding the shaving sharp edge longer than ZDP-189. I have noticed it holds that razor edge longer than most (CRUWEAR is up there too from my simple observations). I wouldn't be surprised if it lost its working edge before ZDP-189 though. Cool testing, although I don't understand why your company and others like it just don't donate those clothes to shelters or Goodwill, it is a shame really :rolleyes:

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Postby michaelm466 » Mon Mar 24, 2014 8:14 am

All cutting was done on items while free hanging (holding knife in one hand and piercing in then pulling item through the knife for clothing. On shoes I just cut in about an inch above the sole the blade would sometimes hit the sole but it wouldn't hit any kind of cutting surface. I think the ZDP had a disadvantage as far as blade geometry goes. Hopefully I'll be able to try this test again with the K390 a couple times to see if I can establish any kind of consistency (though that may be out of reach with the type of media and length of cuts per item changing so much from group of items to group of items)
I haven't done this with any other steels yet, but m390,s90V and M4 will probably be the next ones up perhaps Elmax (ZT560) and S110V (ZT560CBCF and Forums Native) as well.

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Postby wquiles » Tue Mar 25, 2014 5:28 pm

Thanks for sharing :)
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Postby wrdwrght » Tue Mar 25, 2014 5:40 pm

I watch posts like this one with great interest. Thanks.

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Postby Coulro » Tue Mar 25, 2014 7:06 pm

Incredible! Thanks for posting!

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Postby sok » Tue Mar 25, 2014 7:50 pm

Thanks michaelm466, I love these kinds of comparisons.

A Military sprint run in this steel would be off the hook. A small Military sprint run could get ugly.

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Postby TomAiello » Tue Mar 25, 2014 8:22 pm

I'd just like to applaud you for taking what was probably a mindless, boring work task and turning it into something entertaining and educational.

And, yes, K390's edge holding is freakin' insane.

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Postby Chumango » Wed Mar 26, 2014 7:49 am

I agree with nccole on this one...although it might reduce the knife usage (and some fun on the job), it is a shame to throw away perfectly good clothes and shoes. Perhaps this might be brought up to management, I am sure there is a way to donate that would not result in lost sales. The clientele at shelters would not likely shop at your store in any case.

Years ago I knew someone whose job was to collect used clothing and ship it to various countries in Africa and Asia. There is a very large market for clothing like this in the developing world where poverty reigns.

And BTW, I lived in Provo at the time. I really liked it there, though it has grown and changed a lot since then. Used to be that you could go shooting up Rock Canyon and Slate Canyon, which I did on many occasions. I would walk from my dorm across campus and through the neighborhoods to Rock Canyon with my rifle and no one cared. One day it was pouring rain and I stuck my thumb out to hitch a ride and little old lady stopped and picked me up, rifle and all. I hunted pheasants behind the State Hospital, and Chukars on Squaw Peak. I wandered all over those mountains.

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Postby RealKnifeUser » Wed Mar 26, 2014 3:58 pm

Ankerson put Super Blue at 61.5 rc and zdp189 at 65 in the same category in this post:

http://www.bladeforums.com/forums/showt ... -quot-rope
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Postby michaelm466 » Wed Mar 26, 2014 6:01 pm

Chumango wrote:I agree with nccole on this one...although it might reduce the knife usage (and some fun on the job), it is a shame to throw away perfectly good clothes and shoes. Perhaps this might be brought up to management, I am sure there is a way to donate that would not result in lost sales. The clientele at shelters would not likely shop at your store in any case.

Years ago I knew someone whose job was to collect used clothing and ship it to various countries in Africa and Asia. There is a very large market for clothing like this in the developing world where poverty reigns.

And BTW, I lived in Provo at the time. I really liked it there, though it has grown and changed a lot since then. Used to be that you could go shooting up Rock Canyon and Slate Canyon, which I did on many occasions. I would walk from my dorm across campus and through the neighborhoods to Rock Canyon with my rifle and no one cared. One day it was pouring rain and I stuck my thumb out to hitch a ride and little old lady stopped and picked me up, rifle and all. I hunted pheasants behind the State Hospital, and Chukars on Squaw Peak. I wandered all over those mountains.
It's unfortunate we can't, a decision made at the corporate level, apparently the first year the store was open they donated to local Salvation Army/D.I./United Way stores and lost thousands because people would buy the clothes there for 50 cents and return them back to our store for full price.

I've been shooting several times up Squaw Peek, I think people here in general are at least more knife friendly compared to most other places I've been.

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Postby nccole » Wed Mar 26, 2014 7:37 pm

michaelm466 wrote:It's unfortunate we can't, a decision made at the corporate level, apparently the first year the store was open they donated to local Salvation Army/D.I./United Way stores and lost thousands because people would buy the clothes there for 50 cents and return them back to our store for full price.

I've been shooting several times up Squaw Peek, I think people here in general are at least more knife friendly compared to most other places I've been.
Thanks again for the testing. Sorry to keep off topic, but I can't help but draw a similarity to Spyderco seconds and how they notch them so they can know if/when they receive them in for warranty work. They could simply hole punch a pattern in the tags or some other method to identify them as donated, and deny returns on them. I hadn't thought of that reasoning, and I think the real reason is brand exclusivity. Oh well, keep the data coming.

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Postby VashHash » Wed Mar 26, 2014 8:25 pm

K390 is some amazing stuff. I want more, it's a great steel. Fairly easy to maintain the edge and it cuts for a long time. Longer than i care to. I really wish i could get a K390 straight razor but i dunno if i could afford it. It's a lot of fun to test steels though. I need to start dedicating more time to it.

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Postby razorsharp » Wed Mar 26, 2014 8:31 pm

Im getting very excited to try K390.

I have this on the way- K390 ground to 0.008" behind the edge, everything is to my spec (CF bolsters and redwood burl hand picked by me) Hardness is 64HRC ... very excited to get it in hand.

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Postby razorsharp » Wed Mar 26, 2014 8:33 pm

VashHash wrote:K390 is some amazing stuff. I want more, it's a great steel. Fairly easy to maintain the edge and it cuts for a long time. Longer than i care to. I really wish i could get a K390 straight razor but i dunno if i could afford it. It's a lot of fun to test steels though. I need to start dedicating more time to it.
Not sure about the razor, I have this feeling the steel would degrade at 4dps very fast, maybe faster than simple AEB-L as its edge stability will be so low having this many alloys in it. Not to mention it wouldnt get as sharp. (or not as easily)


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