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Thread: Need some help to improve cutting performance of Navaja

  1. #1
    Spyderco Forum Registered User bh49's Avatar
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    Need some help to improve cutting performance of Navaja

    Hi guys, help me out.
    I love Navaja. It has a great look, cool sound, great F&F and ergos. I do not use all of my knives, but this one I loved so much that he has to be carried and used. The first cut was quite simple: I needed to open the pack of paper towel and I noticed that it took some pressure to plunge through plastic and cut it and I realized that grind of the blade is quite thick, especially at the tip. I was wondering if Spyderco can regrind the blade to make it thinner and had no problem to pay. But I was told they will not be comfortable to do this job and even if Spyderco do this modification, that would void warranty. So the best option at that time was to reprofile to 30 degrees, Spyderco rep did not recommend to reprofile to more acute angle due to possible chipping of the edge. I sent knife to Spyderco for reprofing and got it back. It certainly cuts better, but not even close to my hollow grind Persian or Caly3.5, the knives, which I usually carry. Yesterday I had to cut my old garden hose in fairly small pieces. For some reason I thought that this kind of job is what S30V for. But after one cut I switch to Persian, it just cuts much better.
    So I am looking for advise. I am little concern about sending to somebody for regrind because this would void warranty, which I would like to keep, considering carraca issues. Does anybody has experience reprofiling S30V to 20 -24 degrees? How does it hold? Or my wishes for Navaja to cut compatible with Persian and Caly3.5 completely unreasonable?
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  2. #2
    Spyderco Forum Registered User unit's Avatar
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    Why would it void the warranty?

    Personally, I would not want to take S30V much below 30 inclusive because I agree that chipping will likely result unless you use it as a letter opener.

    I might have some suggestions for you, but I would like to gain a better understanding of what you really want to do with the knife. Are you just wanting to brush it across a package of TP and have the plastic cut with little effort? If that is all you want, I might suggest what I call a refined coarse edge. Profile the bevel with a very coarse stone, then strop it about 20 strokes per side with a 1 or 0.5 micron loaded strop (green rouge works fine for S30V).

    This sort of "toothy" edge will work quite well for opening plastic packages!
    Thanks,
    Ken (my real name)

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  3. #3
    Spyderco Forum Registered User bh49's Avatar
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    Ken,
    I use my knives to cut anything I need: branches, cardboard boxes, open letters and so on.
    I never strop and cannot sharpen free hand: I use sharpmaker. Grind on the edge is fairly coarse now, so if instead of strop I will use medium and fine rods, will it work to improve performance? What do you think?
    Roman
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  4. #4
    Spyderco Forum Registered User jabba359's Avatar
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    I haven't used my Navaja as much as I would like for exactly the same reason. It's a bit thick for what I use my knives for. If you don't mind voiding the warranty, I'd recommend having Nick Rossi (on USN) or Brad Southard regrind the knife, taking some material off the blade but leaving your edge at 30 degrees. I don't think you really need to thin out the edge, as it's the mass of material behind the edge that inhibits cutting.
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  5. #5
    Spyderco Forum Registered User The Deacon's Avatar
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    While I can understand your reluctance to void the warranty, given the number of problems with the Navaja's carraca mechanism, I'm of the opinion that, thinning the blade is the only thing that will help significantly. I think that, unless you're talking reducing an edge angle that was over 40, making it more acute will have much less impact on overall cutting performance than decreasing the thickness behind the edge. That's why the Calypso family of knives, and Tom Krein regrinds cut so well, they're consistently thin behind the edge. It becomes a question of which is more important to you, the novel, but relatively useless sound of the carraca, or cutting ability. If the later, I believe Brad Southard could help.
    Paul
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  6. #6
    Spyderco Forum Registered User unit's Avatar
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    Roman.

    I am not very familiar with the geometry of your knife but it is sounding like the thickness may be the issue. For shallow cuts ( like plastic wrap) the geometry behind the edge is less consequence. For cutting cardboard and hoses, it become more important, and for thick things like cheese it becomes paramount.

    Given your resources, i'd suggest sharPenng the knife as best you can then returning to the brown rods for 3-5 light passes per side on the flats. This should add a little tooth. If that is not to your liking (or at least a step in the right direction) you either need a full blade re-grind or a different platform mor noted for slicing.

    I wish you lived close. It' be nice to get together and play with some options.
    Thanks,
    Ken (my real name)

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  7. #7
    Spyderco Forum Registered User chuck_roxas45's Avatar
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    I find a 600 grit finish on my edge will separate tight, thin plastic with a very light touch.
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  8. #8
    Spyderco Forum Registered User
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    I've been thinking about this a lot recently and I feel like the warranty should not be voided for modifications unless they effect what you're claiming against. I want to tap the other side of one of my striders for the pocket clip, but I can't unless Strider does it due to warranty voiding.

    If I tap some screw holes then the blade snaps in half, that should still be covered. If you reprofile your blade and the spring breaks, that should be covered. The two are completely unrelated.

    I understand this isn't how it works, but if I modify a car under warranty the dealer has to prove that my modification caused any issues before they deny my claim.

  9. #9
    Spyderco Forum Registered User angusW's Avatar
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    Roman, I agree that the angle used on the stock Navaja is quite obtuse and was disappointing to use when I first received mine. I brought mine down from over 20 a side to 15 and it's much nicer to use. With my limited experience with s30v, I wouldn't want to go down to 10-12 a side as it's going to chip. I have an old garden hose in the garage. I'm going to cut it up tomorrow with my Navaja and compare it with a few different knives.
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  10. #10
    Spyderco Forum Registered User
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    Did they ever discover what the problem with the Carraca was? Mine still works fine but I must admit as soon as I discovered that my bolsters were unevenly milled the knife got boxed - it was scratching the inside of my hand every time I handled it.

  11. #11
    Spyderco Forum Registered User bh49's Avatar
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    Gents,
    Thank you very much for help. You confirm my thought. Blade need to be regrind to correspond to my taste.
    Roman

    Quote Originally Posted by jabba359 View Post
    I'd recommend having Nick Rossi (on USN) or Brad Southard regrind the knife, taking some material off the blade but leaving your edge at 30 degrees. I don't think you really need to thin out the edge, as it's the mass of material behind the edge that inhibits cutting.
    Thank you. Will do that

    Quote Originally Posted by The Deacon View Post
    It becomes a question of which is more important to you, the novel, but relatively useless sound of the carraca, or cutting ability. If the later, I believe Brad Southard could help.
    Paul, believe or not, I love the sound, but I want to cut.
    How thick the blade behind the edge on your Chaparral? What do you think if I ask to thin out the blade to .020" behind the edge are any danger to chipping?
    Quote Originally Posted by unit View Post
    Roman.
    I wish you lived close. It' be nice to get together and play with some options.
    Thank you. This would be nice. If one day you will visit CT, please let me know. I will invite or meet you for beer or coffee. Your choice.

    Quote Originally Posted by angusW View Post
    I have an old garden hose in the garage. I'm going to cut it up tomorrow with my Navaja and compare it with a few different knives.
    Please, let me know.
    Thank you,
    Roman
    "People sleep peaceably in their beds at night only because rough men stand ready to do violence on their behalf"
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    Any knife without Spyderhole is defective.
    My top choices Native5, G10/VG10 Caly 3.5/3 & C83 Persian Black micarta/bolsters

  12. #12
    Spyderco Forum Registered User unit's Avatar
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    Will do Roman, Likewise, if ever in my area.

    Another solution you could attempt is have someone reprofile the edge to 15 or 20 inclusive, then put on a (not-so) micro bevel. Think of this as a partial re-grind that knocks the shoulders back on the bevel, but retains more of the lateral blade strength. As an added bonus, you can maintain it on your Sharpmaker.

    There is much talk about this voiding the warranty, but I am not sure that is the case. I have a really hard time believing that if the spring breaks, Spyderco is going to tell you to pound sand because you "sharpened" the knife. Now, if you snap the blade...that would probably not be warrant-able, but I can not imagine it would be anyway.
    Thanks,
    Ken (my real name)

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  13. #13
    Spyderco Forum Registered User bh49's Avatar
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    Ken,
    When I contacted Spyderco cs I ask them if they can regrind the blade at my expense. I was told that even if they do regrind, this would void warranty. Later I was told that people who can do this job are not comfortable regrind this blade because it was made at their plant.
    I already sent e-mail to couple people regarding regrind. I can reprofile the edge with my sharpmaker @ 24 inclusive (which certainly improve performance of my Persian) and than put microbevel @ 40. I can try this before I send out.
    "People sleep peaceably in their beds at night only because rough men stand ready to do violence on their behalf"
    George Orwell
    Any knife without Spyderhole is defective.
    My top choices Native5, G10/VG10 Caly 3.5/3 & C83 Persian Black micarta/bolsters

  14. #14
    Spyderco Forum Registered User unit's Avatar
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    Like my sig line says...Learning all the time.

    That is an odd warranty, but it's not my call.

    I'd be inclined to try the 24 inclusive as you mention, but perhaps do not grind all the way to the edge. Thus you will remove the shoulders and retain the most steel. Just work slow and inspect often.

    Do you have a micrometer? I'd be interested in some measurements above the edge bevel in a few spots (tip, belly, flat, choil).
    Thanks,
    Ken (my real name)

    ...learning something new all the time.

  15. #15
    Spyderco Forum Registered User Donut's Avatar
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    I think this is all because of the thickness behind the edge and also maybe the wide grind.

    My HEST Folder came with a 40 degree edge on it, I put a 30 degree edge with no microbevel on it and it is still not the greatest slicer because it is so thick behind the edge.

    If it were me, I would probably check with Brad Southard to see what he thinks would help it. I've heard several people say that he knows what makes a knife cut well.

    In my opinion, you could redo the flat grind and lose the spyder logo, or maybe do a slight convex grind to try and keep the spyder logo on there. Either of these can make the blade behind the edge thinner and I think will improve the cutting performance.
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  16. #16
    Spyderco Forum Registered User hunterseeker5's Avatar
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    Rather than trying something radical like regrinding the entire blade, why not try something a bit more gentle like a convex edge?
    http://www.youtube.com/whatfor5#p/a/u/1/tuT8ROeEg4E

    Something like that can knock down a bit of thickness behind the "edge bevel" but keep the edge angle such that you won't immediately chip it like hell. Of course the mirror polish edge doesn't hurt either. (that particular edge was polished down to .5 micron)

  17. #17
    Spyderco Forum Registered User bh49's Avatar
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    Quote Originally Posted by unit View Post
    I'd be interested in some measurements above the edge bevel in a few spots (tip, belly, flat, choil).
    Tip- .055"
    belly - .038"
    flat - .038"
    near choil - .039"

    I beleive, it was a little thinner before reprofiling, which is understandable because the edge visible wider now.
    "People sleep peaceably in their beds at night only because rough men stand ready to do violence on their behalf"
    George Orwell
    Any knife without Spyderhole is defective.
    My top choices Native5, G10/VG10 Caly 3.5/3 & C83 Persian Black micarta/bolsters

  18. #18
    Spyderco Forum Registered User Blerv's Avatar
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    I would be inclined to carry a Ladybug as well for certain tasks.

    You could have it ground thinner but you always trade something for that performance. Light cars are fast in the corners and don't hold up well when they hit the railing.

    Knowing the downfall of any modification helps justify the choice to perform said modification or leave it stock. Assuming drastic changes can be made to improve certain aspects w/o the chance of adding vulnerability is silly.

    PS: My reground ZDP Stretch eats zip ties for lunch. No chipping either. Go figure.
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  19. #19
    Spyderco Forum Registered User bh49's Avatar
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    Quote Originally Posted by Blerv View Post
    I would be inclined to carry a Ladybug as well for certain tasks.
    I have Ladybug on my keychain , but I have keys on me only when I drive. Still I never had cutting issues with any of my EDCs during Spyderco addiction era (Native, Adventura, Endura, Delicas, R2, both Persians, Caly3, Caly3.5, Kopa). In fact Navaja made me think about knives and EDC choice.
    The good news for me and some other people that Tom Krein will star regrind again in couple month. While I wait I can play with knife a little. Yesterday I spent more than an hour to reprofiling the blade. Not there yet. Hopefully I will have more time tonight or tomorrow. The goal is reprofile @ 24, smooth shoulders, microbevel at 40.
    "People sleep peaceably in their beds at night only because rough men stand ready to do violence on their behalf"
    George Orwell
    Any knife without Spyderhole is defective.
    My top choices Native5, G10/VG10 Caly 3.5/3 & C83 Persian Black micarta/bolsters

  20. #20
    Spyderco Forum Registered User angusW's Avatar
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    Well Roman, I went out to the garage tonight with 6 Spydie's to cut up an old garden hose. All of them are sporting 15 a side. The only difference is the Navaja has a convex grind mostly due to my inability to keep it perfectly level when I was changing the bevel angle. All of them are fairly sharp, able to cut newsprint fairly good with the same level of cutting ability. They all went through the garden hose with pretty much the same degree of pressure. I think the convex edge of the Navaja really makes a difference in how it goes through material. I am by no means that good at sharpening but using a wedge like unit came up with makes it a pretty easy adventure. My Navaja really is a joy to use now.

    Here's the knives I used tonight to cut the hose.

    Navaja
    Sage 1
    Military CTS-XHP
    Paramilitary 2 CTS-20CP
    Manix 2 CTS-BD30P
    Mule Super Blue

    Here's a pic of the Navaja right after I finished changing the bevel angle.

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