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Thread: CBN Rods

  1. #1
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    CBN Rods

    I normally prefer to wait longer before discussing something to confirm/ensure conclusions, but since a few people asked, here is some information. Please be aware that the data is very sparse at this stage so don't draw overly strong conclusions from it. All work was done using the Sharpmaker with the 20 dps setting (for maximum operator benefit) .



    This is a high magnification shot of the surface of a medium rod, the scale is in the picture (credit to Clay Allison for convincing me to stop being so lazy and to put it in there). Here is the CBN rods at the same magnification :



    The grit size difference is obvious, you can even measure the exact grit size of the CBN as you can just see the grains clearly. Note as well they are fairly evenly distributed and not subject to extreme mass clumping. This is confirmed if you just feel the rods, they are rough yes, but they are not highly irregular.

    Note as well that the 400 mesh or sieve rating appears to be correct as the particles are of the order of 40 microns which is the approximating micron rating for 400 mesh.

    For reference, here is a 240X SPS-II waterstone :






    This is the edge on a Mora #1260 (the number doesn't mean anything, it is just the model number) which is 1095 at 58-59 HRC (as spec). It has been flattened and the edge apexed with a Bester 700 grit waterstone, using the hone-to-dry method to maximize the edge finish. Note the :

    -uniform scratch pattern
    -even edge line
    -small irregularities

    I then cut the edge off by making three slices into the same stone to mill a flat on the edge. This is the result of just 10 passes per side on the CBN :



    The edge is brought to an apex immediately and will slice newsprint but won't shave and the edge has some pieces knocked out of it as would be expected. Here is the result of 6 more passes which are done using ultra-light honing (5-10 grams) on the CBN rods :



    Note the edge is refined and now it will shave, but it is really coarse, even a wet shave isn't likely to be comfortable. I cut the edge off again (same process, 3 cuts into the 700 grit Bester) and just for comparison apexed it with the medium rods. This time it took 130 passes per side :



    The edge is significantly more polished and shaves well and does all the things you expect from the Spyderco medium rods (3-finger sharpness test passes readily). Note that the bevel now is about 0.1 mm side and you can see it by eye.

    As another comparison, to see if you could jump from the CBN right to the medium rods I cut the edge off again (same process, three passes into the 700 grit bester) and then apexed the edge with the CBN rods. As the edge was much thicker/wider now it took 30 passes per side to apex.

    (I don't have the diamond rods, if I did I would have interjected them here).

    I then switched to the medium rods. After 10 passes per side there was a significant difference in finish, after 30 passes per side it was back to the Spyderco medium rod finish. To clarify now, I am working on a very narrow bevel, it is still only about 0.1 mm or so wide.

    In short :

    -the rods are fairly coarse, a 400 mesh/grit rating is a decent approximation to the type of finish
    -they cut much faster than the medium rods
    -in order to jump from the CBN to medium rods the bevel would have to be very narrow
    -the edge from the CBN rods can be sharp, it isn't just shaping only
    -the abrasive is well distributed

    A immediate recommendations / observations :

    -use the CBN rods to set the relief only, use the medium rods as the micro bevel

    If the diamonds are inbetween then you could use them. If you try to polish the CBN bevels with just the medium rods you are likely going to be at it awhile. I will measure this later.

    In regards to issues, there is only one :

    There were a couple of points where the surface was rough enough to snag the edge. Do not, and this is critical, try to resolve this by just grating the edge hard against the rods, this will just tear the grit off the surface. For the first sharpening use the highest carbide knife you own which is fairly dull (or that you want to reset the angle). Work it light and slow and this will even out any of the coarse spots.

    (the reason that you do not want to use a low carbide knife is because it will be cut much easier which means much deeper and you could just pull out the high spots and you want to wear them down rather than just pull them off or crack off a large piece)

    If there is any thing in particular of interest just let me know.

  2. #2
    Spyderco Forum Registered User D1omedes's Avatar
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    Thank you for the sharing of the data you have discovered so far, Cliff. I find any possible new additions to the Sharpmaker very exciting.

    Are the CBN rods similar to the alumina ceramics of the brown and white rods? In essence, will CBN wear away over time or break off (as has been reported on the diamond rods)?

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    Thanks for the info. Love macro pics!

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    Can we see some non macro shots of the CBN rods?

    I hope Spyderco puts out some 800 mesh CBN rods.

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    Thanks, Cliff... much appreciated review.

    I will pick these up as soon as I know where to get a set!

  6. #6
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    Quote Originally Posted by Henry - get both View Post
    Can we see some non macro shots of the CBN rods?


    and :




    I hope Spyderco puts out some 800 mesh CBN rods.
    Solid CBN would be interesting, cost would be an issue.

    Quote Originally Posted by D1omedes View Post
    Are the CBN rods similar to the alumina ceramics of the brown and white rods?
    The alumina stones are solid sintered products meaning that you are unlikely to wear them out in your lifetime, or in fact even wear them enough they need to be lapped, the CBN ones are a plated product, there is a single layer of CBN which has a nickle electroplated bond. This is a very common form of the abrasive (along with the solid vitrified bond).

    In essence, will CBN wear away over time or break off (as has been reported on the diamond rods)?

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    Spyderco Forum Registered User bearfacedkiller's Avatar
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    I wonder how soon I can stop into the SFO and pick a set up? Thanks cliff, again. :-)

    I might just put, "Thanks Cliff" in my signature. Save myself some time. lol!!
    -Darby

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    Spyderco Forum Registered User jabba359's Avatar
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    Quote Originally Posted by Cliff Stamp View Post
    The edge is significantly more polished and shaves well and does all the things you expect from the Spyderco medium rods (3-finger sharpness test passes readily). Note that the bevel now is about 0.1 mm side and you can see it by eye.
    I don't recall reading before what the 3-finger sharpness test is. Could you please elaborate?

    Thanks for sharing your impressions on these.
    -Kyle


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    Quote Originally Posted by jabba359 View Post
    I don't recall reading before what the 3-finger sharpness test is. Could you please elaborate?

    Thanks for sharing your impressions on these.
    Kyle-
    It's Murray Carters test...

    Should be able to Google from there...

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    Spyderco Forum Registered User jackknifeh's Avatar
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    Quote Originally Posted by jabba359 View Post
    I don't recall reading before what the 3-finger sharpness test is. Could you please elaborate?

    Thanks for sharing your impressions on these.
    The 3 finger test was started (as far as I know) by Murray Carter (cartercutlery.com). He has a description of how to do it and what to look or feel for. To get any benefit from the test you will need to perform it on about every knife you handle. A lot of the info the test will tell you is actually a comparison with other knives. You need to perform the test on knives of very different sharpness and edge type (toothy vs smooth) to be able to feel what the test shows. Once you can tell the difference you can determine the sharpness of an edge by doing this one test. Personally, the only thing I can determine by performing the test is if the edge is toothy or smooth. Both could be very sharp. A dull edge will allow the skin to slide along the edge but so will a razor sharp smooth edge. The toothy edge however will grab the skin creating resistance to being able to slide the skin along the edge. Yup, along the edge, not across it. Don't worry, you won't cut yourself if you do it right. Read Mr. Carter's explanation for accuracy's sake.

    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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    Thanks, Jack.

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    Thanks Cliff.

    Im looking forward to trying these. Back in 2007 Sal described the diamond triangles as 400 mesh, 10th post in this thread:

    http://www.spyderco.com/forums/showt...DMT-extra-fine

    A long term comparison between the diamond and CBN triangles would be interesting to me.

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    Quote Originally Posted by jackknifeh View Post
    The 3 finger test was started (as far as I know) by Murray Carter (cartercutlery.com).
    He didn't start it, but he certainly popularized it and described it with more detail than most.

    It is very common for people to argue that you can judge sharpness by how an edge feels, what Carter did was fairly critical for a few reasons.

    a) he realized that a knife can shave and still not be sharp as the edge can be rounded and thus slice very poorly

    b) there needs to be some way to quantify how an edge feels to allow one person to communicate it to another

    Most people don't do the second and don't understand the first part.

    The test is extremely basic and it is no more than this :

    -you put your fingers on the edge of the knife and see if you can draw them along the edge and not get cut

    When people read that it sounds insane, of course you can't do that, what happens if a knife is sharp then you would slice your fingers open. What Carter argues is if the blade is really sharp then you will not draw your fingers at all because you will stop. This sounds frankly idiotic but you can actually do it and it does allow you to readily separate a knife which has a rounded edge vs one that doesn't.

    Now can you slice your fingers open, sure - but I knew a guy who ran over his own head while driving a car so lots of things are possible.

  14. #14
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    Quote Originally Posted by Henry - get both View Post

    A long term comparison between the diamond and CBN triangles would be interesting to me.
    I will see if I can't find a set of the diamond rods.

  15. #15
    Spyderco Forum Registered User Blerv's Avatar
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    So these are more coarse than the diamonds?

    If that's accurate it's very interesting. Would you say they are a suitable replacement or simply another tool in the Sharpmaker belt?

    Thanks a ton, Cliff!
    Blake

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    http://www.handgunlaw.us/documents/USKnife.pdf

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    Spyderco Forum Registered User jabba359's Avatar
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    Thanks everyone for clarifying the 3-finger test. Surprisingly, I hadn't heard of it before. Guess I learn something every day. I suppose the name comes from how many fingers I would have left if I do the test wrong!
    -Kyle


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  17. #17
    Spyderco Forum Registered User Clip's Avatar
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    Quote Originally Posted by Cliff Stamp View Post
    but I knew a guy who ran over his own head while driving a car so lots of things are possible.
    I'm tempted to say pics or it didn't happen...but I'll just take your word for it.
    Click here to zoom: Under the Microscope

    Manix2, Elmax MT13, M4 Manix2, ZDP Caly3, ZDP Caly Jr, SB Caly3.5, M390 Para2, Cruwear MT12, Techno, XHP MT16, South Fork, SB Caly3, Manix2 Ltwt, Salt I, 20CP Para2, Military Left Hand, Perrin PPT, Forum Native5, Squeak, Manix 83mm, 440V Military, Gayle Bradley, Swick3, Lil' Temperance, Cruwear Military, VG10 Jester, Terzuola SlipIt, XHP Native Ltwt, Domino, CPM154/S90V Para2, SB Stretch, D2 Para, Dfly2 Salt, Tasman Salt

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    Spyderco Forum Registered User bearfacedkiller's Avatar
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    Quote Originally Posted by Blerv View Post
    So these are more coarse than the diamonds?

    If that's accurate it's very interesting. Would you say they are a suitable replacement or simply another tool in the Sharpmaker belt?
    I am wondering the same thing. I already have the diamond rods and wonder what the difference would be. I'll probably get a set just to see for myself anyway.
    -Darby

  19. #19
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    Quote Originally Posted by Clip View Post
    I'm tempted to say pics or it didn't happen...but I'll just take your word for it.
    I did not witness it but as the story goes ... he came home one night fairly drunk, tried to steal his fathers car, was caught in the act, jump out with the car in gear, slid and fell back and the tire skimmed the side of his head and ripped off a fairly large chunk of hair. Now he could have just made it all up to explain why he suddenly was missing a big piece of hair and skin - but if he did, good on him for that anyway as it was pretty entertaining.



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    Do you have any data on how these compare to the diamond rods Cliff?

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