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Thread: 3 finger sharpness test explained from cartercutlery.com

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    Spyderco Forum Registered User jackknifeh's Avatar
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    3 finger sharpness test explained from cartercutlery.com

    We have discussed this a bunch here but the 3 finger test came up in another thread but I want to put this here because it was off the subject of the other thread.

    I had emailed them explaining my understanding of the test and asking for clarification. Here is the reply I received this afternoon.

    Hello Jack,

    Thank you for the email! Hopefully we can clear up any confusion you have. Firstly, the goal of the three finger test isn't to understand how much pressure is needed in order to instigate a cut, instead it is to experience a sensation that (when your fingers are pressed lightly upon the primary edge) your brain tells you, 'if you move your fingers, you will be cut'. This is the sensation of a truly scary sharp edge. The easiest way for you to experience this would be to send us a knife and have Murray sharpen it for you. If you are a Knife Care and Maintenance Subscriber, send us a knife with good quality steel and Murray will sharpen the blade for you, free of charge. All we ask is that you provide return shipping, which is $15 (Priority USPS). When your sharpening your blades, what is the process? Do you finish by stropping on leather?

    Thanks again for the email and feel free to contact us if you have any further questions or concerns.

    Sincerely,

    Jason
    for Murray Carter

    Guess I have some work to do on my sharpening skill because I can always feel confident to slide my fingers along my edges. I know I need to use extremely light pressure but I have NEVER felt like I was absolutely going to get cut if I slid my skin at all. I know it wouldn't take much pressure but still I need to know what they really mean. That means I need to have a knife that they say passes the 3 finger test. You know what that means? I think I'm goint to send him a knife. Which one!??? Which of the knives that I have would I be less devistated over if it were to get lost? This is a tough one. I will think on it. The one I WANT to send him is my GB. That knife fits into two categories regarding this. It is the one I would want most to come back sharper than anything I've seen. OTOH, it's the one I would be MOST devistated if it were to get lost. Honestly, I have never had anything get "lost in the mail". Nothing important enough to remember anyway.

    BTW, Jason mentioned if I were a "knife care and maintenance" sucriber. That means I at least signed up for the free 7 or 8 tips about knife maintenance Mr. Carter sends out in emails to whoever asks. So the offer of a free sharpening (except for $15 return shipping) comes to anyone who does that. Also, there's a lot of good info in the emails. I recommend getting them. They are free. I'd love to get one of his knives but they are a bit (by double at least ) out of my price affordability.

    Anyway, I figured a "quote" from the web site would be good regarding this test.

    Jack

    My EDC for a while. Stretch with carbon fiber handle, Chaparral 2, Dragonfly 2 with kirinite MOP handle, Manbug with bolster/red bone handle. Super blue/420J1 blades on all three (except Chaparral).

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    Spyderco Forum Registered User Evil D's Avatar
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    I must have dead fingertips, because I can do this with any of my knives or even a razor blade and not feel like I'm going to get cut. I may have to send a knife to Murray just to see, but honestly I'd be more concerned with how he changes my bevel than anything lol.

    Is it evil of me that I just had a daydream of sending him something like Rex 121 just so he has to work his butt off to sharpen it?

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    Spyderco Forum Registered User paladin's Avatar
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    Quote Originally Posted by Evil D View Post
    I must have dead fingertips, because I can do this with any of my knives or even a razor blade and not feel like I'm going to get cut. I may have to send a knife to Murray just to see, but honestly I'd be more concerned with how he changes my bevel than anything lol.

    Is it evil of me that I just had a daydream of sending him something like Rex 121 just so he has to work his butt off to sharpen it?
    I was just thinking the same thing, lol

    If you have a k390 Mule that may be a good specimen to send Jack.

    I'm probably a little more jaded than your garden variety ELU-- but honestly Jack, if Murray Carter don't answer his own emails, How could we confirmed "he" sharpened your knife? You may drive yourself insane with just the implications...

    What if..."Jason" really sharpened your knife "for Murray?" Or if "Bruce" sharpened it for "Jason for Murray?"
    Have Kiwi, will travel...wire Paladin...Hotel Carlton, San Francisco

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    I'm not a sharpening expert but I can get an edge sharper than I need it to be, and I'm not going to try this with my knives.

    To me this is the definition of "scary sharp"- when you touch the edge with your finger and you think it will cut you if you move, you pull your finger away because you are scared to touch it anymore.

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    Spyderco Forum Registered User 78lilred's Avatar
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    Grit depends on the 3 finger sticky for my knives, fine ceramic on my double stuff still grabs, EF diamond plate(9 micron) gets a lot of "drag" if applying light pressure and attempt to slide/move. 400 grit from my mold master gets a pretty aggressive edge but not as much sticky as just serrations since its ~40microns. Fingertips are also pretty sensitive/soft, thumbs not so much.
    M390 Para2, CTS-XHP Para2, CTS-204P Para2, Gayle Bradley, Techno, Bob T Slipit, M390 Mule, Southard, Southfork, Air, Tuff, ZDP Caly 3.5.

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    Spyderco Forum Registered User jackknifeh's Avatar
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    Quote Originally Posted by paladin View Post
    I was just thinking the same thing, lol

    If you have a k390 Mule that may be a good specimen to send Jack.

    I'm probably a little more jaded than your garden variety ELU-- but honestly Jack, if Murray Carter don't answer his own emails, How could we confirmed "he" sharpened your knife? You may drive yourself insane with just the implications...

    What if..."Jason" really sharpened your knife "for Murray?" Or if "Bruce" sharpened it for "Jason for Murray?"
    I thought about that too. I replied to the email saying I'd send a knife to them. Jason replied that Murray was out and would be back around the 1st. Murray would sharpen the knife and probably have it in the mail back to me in a couple of days. So Jason is saying Murray will be the one sharpening the knife I send. I'm going to trust this. No other option really but on the tasks in his business that reflect directly on Carter Cutlery I'm sure he either does it himself or the person who does sharpen the knife will get it as sharp as Mr. Carter would. I assume Mr. Carter would be sure of that. So even though I thought of it I'm going to proceed with trust. But even if someone else sharpens it I don't care as long as it is the same quality work as Murray would do.

    I've decided to send them either the GB or a knife a very kind forum member made and then later gave to me. Both have M4 steel and I use both so the edge is important to me on both. Or, should I get the knife back and not use it so I can always have a knife that sets the goal of sharpness. That's a consideration I may consider. In my email I mentioned these three steels, VG-10, S30V and M4. Jason replied with high praise for the M4 and that's all he said.

    So when I get the knife back I will have a knife that passes the 3 finger test of sharpness and I'll try it myself. Hope I learn something. Not as concerned with doing the test as I am with seeing the edge on the knife.

    Jack

    My EDC for a while. Stretch with carbon fiber handle, Chaparral 2, Dragonfly 2 with kirinite MOP handle, Manbug with bolster/red bone handle. Super blue/420J1 blades on all three (except Chaparral).

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    Spyderco Forum Registered User SkullBouncer's Avatar
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    A good time back, Gail Glesser at SFO showed me the best way to perceive proper edge sharpness and overall uniformity I've seen and used yet, this on one of my original VG-10 prototype Chinook test piece I brought in one day. She personally took the time to guide my hand in hers as I used a Sharpmaker for the first time-- she did a fabulous job obviously, and she demonstrated her sharpness test technique as laying the index finger lightly down the length of the edge / blade profile, in this case a crescent from blade tip at 1st knuckle underside out to the fingertip placed incrementally toward the blade base with very slight side to side and rolling pressure, and the use of a loupe. Very accurate.


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    Last edited by SkullBouncer; 03-25-2014 at 09:34 PM. Reason: Gramma'

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    I have always noticed there is a big difference in my success at the three finger test when sharpening at different grits. When I'm doing S30V or VG-10 with the brown rods, I feel scared to touch the edge because the toothy edge just grips my fingers. And don't even get me started on a new edge fresh off the diamonds.

    However, when I'm sharpening Super Blue up to the Ultra Fines, the edge is smooth enough I can lightly run my fingers on the edge and feel reasonably sure that I won't see blood.

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    Spyderco Forum Registered User jackknifeh's Avatar
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    Quote Originally Posted by Invective View Post
    I have always noticed there is a big difference in my success at the three finger test when sharpening at different grits. When I'm doing S30V or VG-10 with the brown rods, I feel scared to touch the edge because the toothy edge just grips my fingers. And don't even get me started on a new edge fresh off the diamonds.

    However, when I'm sharpening Super Blue up to the Ultra Fines, the edge is smooth enough I can lightly run my fingers on the edge and feel reasonably sure that I won't see blood.
    Your thinking about the test is EXACTLY the same as mine until today. Cliff seems to be the only one who had or has the most accurate understanding. Read the reply I posted again. I understand what Jason is saying I think. However, even though I think my knives are very sharp after sharpening them, they won't pass the test as I think I understand it now. So I'm going to send a knife to be sharpened to see what and feel what Murry says passes the test. When I get the knife back I should know what an edge that passes the test feels like. After I have a good understanding of the test and have a better idea of how much I need to improve I'll post absolutely nothing. I won't share any new knowledge. Joking.

    Jack

    My EDC for a while. Stretch with carbon fiber handle, Chaparral 2, Dragonfly 2 with kirinite MOP handle, Manbug with bolster/red bone handle. Super blue/420J1 blades on all three (except Chaparral).

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    Spyderco Forum Registered User SkullBouncer's Avatar
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    Aaand, I need to add, I will now be looking into the three finger test as well. Thanks for the thread, all.



    Stay Sharp --
    -- SB / Bruce

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    Quote Originally Posted by jackknifeh View Post
    Your thinking about the test is EXACTLY the same as mine until today. Cliff seems to be the only one who had or has the most accurate understanding. Read the reply I posted again. I understand what Jason is saying I think. However, even though I think my knives are very sharp after sharpening them, they won't pass the test as I think I understand it now. So I'm going to send a knife to be sharpened to see what and feel what Murry says passes the test. When I get the knife back I should know what an edge that passes the test feels like. After I have a good understanding of the test and have a better idea of how much I need to improve I'll post absolutely nothing. I won't share any new knowledge. Joking.

    Jack
    Hmm. Upon a closer reading I see that is true. I guess I need to get better at my sharpening. And at physics. Who knew knife-knuts had it so hard in keeping with their addictions

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    Someone mentioned sending in a GB- out of the box my GB was extremely sharp. If someone has an unused GB maybe they could do the test with it.

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    Spyderco Forum Registered User jackknifeh's Avatar
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    Quote Originally Posted by bdblue View Post
    Someone mentioned sending in a GB- out of the box my GB was extremely sharp. If someone has an unused GB maybe they could do the test with it.
    Spyderco knives come very sharp out of the box. I don't think they are sharp enough to compare with a hand sharpened knife done by a very good knife sharpener though who has done his best on a knife. I only got two Spyderco's that were very very very sharp. Stretch blue handle w/zdp and the Michael Walker w/zdp. I don't think any knife company can claim every knife they sell is as sharp as a good sharpener can get them. I'm not trying to slam any company, especially not Spyderco who make my favorite knives. I just don't think you can compare the edge of knives sharpened in a production line with the edge sharpened by a skilled sharpener who takes his time on each knife. A few Spyderco's come out screaming sharp and a few come out a bit on the dull side. Most are very sharp and ready for use. Sharpness out of the box is great but not all that important because every knife needs to be sharpened sooner or later. Anyway, I think what I'm saying is Spyderco's average sharpness is not sharp enough to match the edge Murray Carter (and other's) can put on a knife. Just my thinking at the moment. I'll know more when I get the knife back after Mr. Carter sharpens it.

    Jack

    My EDC for a while. Stretch with carbon fiber handle, Chaparral 2, Dragonfly 2 with kirinite MOP handle, Manbug with bolster/red bone handle. Super blue/420J1 blades on all three (except Chaparral).

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    I'm wondering if the 3-finger test is affected by an individual's skin?

    I've noticed that when my fingers are wet, a knife that did feel scary-sharp no longer feels sharp at all, for instance when washing off my Dragonfly Salt, while my hands are all wet it just doesn't feel sharp. After my hands and the knife are dry again, I can feel the "bite" of the edge again.

    So would someone with naturally more moist skin not feel the edge to be as sharp?
    Which Knife, A or B? get Both! (and C, D and E)

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    Spyderco Forum Registered User Evil D's Avatar
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    Quote Originally Posted by rodloos View Post
    I'm wondering if the 3-finger test is affected by an individual's skin?

    I've noticed that when my fingers are wet, a knife that did feel scary-sharp no longer feels sharp at all, for instance when washing off my Dragonfly Salt, while my hands are all wet it just doesn't feel sharp. After my hands and the knife are dry again, I can feel the "bite" of the edge again.

    So would someone with naturally more moist skin not feel the edge to be as sharp?
    For that matter if you have very thick calloused skin, you may not feel the same sensation, and perhaps could even take very light cutting before you would ever feel pain or see blood. I have all the respect in the world for Murray and will bow to his superior sharpening skill, but I just don't believe in this test for sharpness. There must be more controlled ways with far less variables.

    SHARPEN IT LIKE YOU LOVE IT, USE IT LIKE YOU HATE IT
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    Spyderco Forum Registered User SolidState's Avatar
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    I'm going to bring this up with him at his sharpening workshop at the OKCA to see what he says. I'm scared to show him my knives though, cause I know they're not up to spec.
    "Nothing is so fatal to the progress of the human mind as to suppose that our views of science are ultimate; that there are no mysteries in nature; that our triumphs are complete, and that there are no new worlds to conquer."
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    Spyderco Forum Registered User jackknifeh's Avatar
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    Quote Originally Posted by SolidState View Post
    I'm going to bring this up with him at his sharpening workshop at the OKCA to see what he says. I'm scared to show him my knives though, cause I know they're not up to spec.
    It would be interesting to hear what he says. If you do bring it up don't forget to post his thoughts here please. He might share some of his wisdom with you if you show him a knife you sharpened. Might as well take the opportunity to learn. I know what you mean though. I'm going to send him a knife of mine and while Ihope to learn from him I also don't want to hear him tell me I'm the worst knife sharpener in the world.

    Jack

    My EDC for a while. Stretch with carbon fiber handle, Chaparral 2, Dragonfly 2 with kirinite MOP handle, Manbug with bolster/red bone handle. Super blue/420J1 blades on all three (except Chaparral).

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    Spyderco Forum Registered User MadRookie's Avatar
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    Quote Originally Posted by Evil D View Post
    For that matter if you have very thick calloused skin, you may not feel the same sensation, and perhaps could even take very light cutting before you would ever feel pain or see blood. I have all the respect in the world for Murray and will bow to his superior sharpening skill, but I just don't believe in this test for sharpness. There must be more controlled ways with far less variables.
    You echo my sentiments exactly!


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    Spyderco Forum Registered User Revival's Avatar
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    Quote Originally Posted by Evil D View Post
    For that matter if you have very thick calloused skin, you may not feel the same sensation, and perhaps could even take very light cutting before you would ever feel pain or see blood. I have all the respect in the world for Murray and will bow to his superior sharpening skill, but I just don't believe in this test for sharpness. There must be more controlled ways with far less variables.
    Exactly! Its not something I want to experiment with either.

  20. #20
    Spyderco Forum Registered User Evil D's Avatar
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    Here's how it's really done


    SHARPEN IT LIKE YOU LOVE IT, USE IT LIKE YOU HATE IT
    ~David

    Official plea to Sal: Can we PLEASE get a DLC Yojimbo 2? PLEASE!!?

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