Beiträge von kwakster

    suomi70: This one came out a little less than perfect as i couldn't get the point exactly in the middle this time, but things like that are dependant on the "form of the day", as it's all freehand work.
    On these blown-up pics it looks worse than in real life though.


    The reason why i started this thread was because i was wondering if Sebenza owners on this forum had anything to contribute regarding the edge retention of their pre- or post 2013 Sebenza models, as somewhere during that year CRK seems to have decided to harden their blades to 59-60 HRC instead of the usual target hardness of 58-59 HRC.


    On the Dutch forum there are at least a few owners who were less then satisfied with the edge retention of their beloved Sebbies, especially when the edge angle was taken down to +/- 30 degrees inclusive, an angle that can be considered a good rule of thumb when sharpening most modern knife steels.
    Spyderco for instance specifically target their edges to come out at that angle after factory sharpening.

    Now that is a very nice job, just like it could have come directly from CRK.
    You should show this in the CRK subforum on Bladeforums as well, i'm sure more people would like to see this.

    Sebenza's can be easily dis-assembled & assembled by the end user by design, that's also why they come from CRK with a hex key.
    Although most of these knives probably end up unused in display cabinets, only to be taken out to be fondled and open an envelope with, there are also many that see actual use in all kinds of environments.
    One example is hunting: the fact that the knife can be disassembled & cleaned thoroughly (even sterilized if need be) is a true bonus, otherwise you could end up with a real stinker the day after you've butchered a deer with it,

    If you're sure that you've put the knife together correctly, then it could be that the pivot bushing is just a hair too long.
    The solution is to take it out and polish both ends a tiny bit (in small steps, and measure in between with a micrometer to make sure that you don't overdo it) in a figure 8 on (for instance) a Spyderco fine ceramic bench stone.
    I've done this procedure quite a few times for owners who had the same problem.


    A good check to see if this could be the case is to open the blade fully while keeping the lockbar from locking it.
    If in that position your blade has play then it's almost surely the pivot bushing.


    In this second part of a documentary about CRK the procedure to polish the pivot bushing is shown from about 36:00 minutes onward:
    Notice she uses wet & dry paper over a flat steel plate.


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    I've sharpened quite a few Sebenza's for others, and how i sharpen them is based on both personal experience and user feedback.
    On older ones i've learned that the lowest angle i can reprofile them to lies around 35 degrees inclusive, and that i have to keep the edge finish rather coarse to still have quite good edge retention.
    On newer ones i can lower the edge angle to around 30 degrees inclusive, and i also can refine the edge more, yet still have good edge retention.
    Other people may have other ideas, but this is what i've found to work well.


    Yesterday i did this regular Sebenza from 2005 in S30V steel, which is the favorite folder of a professional hunter.
    The old factory edge was kept more or less sharp by him with stropping only, and the edge angle measured 35-40 degrees inclusive on the straight part and well over 40 degrees inclusive from the belly to the tip.
    I reprofiled the edge to an even 35 degrees inclusive from heel to tip on my Rubber Wheel covered with 230 grit diamond powder (covered in wax to prevent any damage due to overheating), and only removed the burr with the Tormek leather wheel coated with 1 micron diamond compound.
    This removes the burr gently but efficiently, while at the same time leaving the scratch pattern intact as much as possible to preserve bite (something i specifically aim for)
    The Rubber Wheel has a tiny amount of "give" in it's surface which provides for an ever so slight convexity in the new edge, and the use of diamonds makes sure that the vanadium carbide particles in the steel are cleanly cut.
    The resulting coarse edge both favors the S30V steel type and the actual use it will see in the hands of the hunter, and it's treetopping sharp with lots of bite.


    No "before" pics this time (i forgot), but below are the result pics i also sent to the owner.






    Spyderco Southard with CTS-204P blade, which has been in use for a few years now with a Dutch scout leader.
    It has already been sharpened several times by him on stones, plus two times by me on Paper Wheels (once up to 6 micron diamond compound, and once up to 15 micron diamond, the latter performing noticeably longer for the owner)


    This time the knife was reprofiled from about 30 degrees inclusive to 25 degrees inclusive with a standard Paper Wheel with 220 grit SiC, then deburred with a second Paper Wheel with 0.25 micron diamond compound.
    This produces a polished semi-coarse edge with an aggressive bite, as the knife is going to be used to cut a lot of 10 mm polyprop rope in the coming weeks.
    You can click the pics 2 x for a bit more detail.



    Update:


    The owner just informed me how the edge on his Southard is doing so far.
    He had used the tip of the knife to cut open about 50 dusty/dirty cardboard boxes filled with porcelain mugs, and this resulted in blunting that tip to a point that it could only barely cut copy paper.
    But according to the owner this was most likely due to the fact that the tip hit the mugs every now & then.


    After all 50 boxes were opened & emptied the Southard was used to cut down each box, which he measured to be a total of about 80 meters or 262 feet of cardboard.
    Afterwards the edge was still able to easily shave the hair from his legs (except about 15 mm of the tip), and the owner feels that the knife isn't due for a touch-up yet.
    He also noticed that the CTS-204P steel holds this edge noticeably longer than the S30V steel in his Spyderco Sage, which he had sharpened himself and used earlier for the same job.

    The knife was lent to professional sous-chef Patrick for about a month, and below are his findings.
    I translated what he mailed me from Dutch into English as precise as i could:


    Update 1 (after 1 week of use):


    I used the knife for 4 consecutive days straight as my only knife, and then for 2 days for odd jobs in between.
    The edge is still reasonably sharp as long as i keep slicing, but when i use it the way i was taught in chef school (like a locomotive) i notice it is less sharp than in the beginning.


    Here is a list of things i cut with it during those 6 days:


    Day 1:


    6 pineapples
    2 melons
    14 kilo steak
    12 kilo rhubarb


    Day 2:


    3 kilo peaches
    4 kilo salmon
    1 kilo onions


    Day 3:


    1 kilo of salted ham
    1 kilo feta cheese


    Pictures of the knife, taken by Patrick on day 3:



    Day 4:


    10 kilo large carrots
    3 kilo onions
    2 kilo tomatos
    2 kilo cucumber


    The knife cuts well, but what is remarkable is that when i cut like i was learned i can feel that the knife chooses it's own direction, like a knife sometimes does when the tip is bent.
    (an a-symmetric blade can have a tendency to do that in certain situations - kwakster)


    But as you can see i did both rougher & finer work, and the edge remains in very good shape in my opinion.


    **********


    Update 2 (after a month of use):


    I have been using the knife on every single working day (5-6 days in one week), and i think the edge is now come to the point where it doesn't get any more blunt.
    I didn't notice any difference while cutting and i also can't see any changes in the edge with the naked eye.
    It is exactly as you told me: i can still cut tomato's with it !
    But only with a slicing motion, as when i try a different cutting technique i can notice that the edge is less sharp.


    All in all i think it's a very nice knife (which took me a while to get used too)



    BTW: Sous-chef Patrick usual knife is a Sakai Takayuki VG10 Santoku 18cm

    The knife has been used for about a month during our holiday in Germany & Austria for cutting all kinds of food on a simple plastic cutting board.
    It performed perfectly until one of the last days i tried to slice one of those large German breads: very good food, but these have quite hard crusts.
    Parts of the edge rolled a bit, but no chipping as i more or less had expected.


    Back at home i resharpened the edge in 3 steps: Rubber Wheel with 230 grit diamond powder, Paper Wheel with 15 micron diamond compound, Paper Wheel with 1 micron diamond compound (deburring)
    The result was a treetopping sharp edge, and in this condition the knife was then loaned for about a month to a professional chef.
    More to follow.

    This brand new Endura ZDP-189 sadly had a less than optimal factory edge, and since this beautiful steel deserves better i reprofiled & sharpened it myself.


    My guess is that these knives are belt sharpened and then have the burr stropped of on a buffer.

    On this knife however it seemed like the buffer ran out of cutting compound (or the sharpener just did a sloppy job), as through my loupe i could see remains of a burr almost along the entire edge. (some of it is partly visible in picture 2)

    Due to this the sharpness was of course severely lacking.

    I also measured the edge angle to be 35 degrees inclusive, which i think is a bit too large for a folding knife in ZDP-189 steel.


    Before sharpening:



    First i removed the old apex by cutting a few times straight into a silicon carbide stone, then reprofiled the edge to a slightly convex ~ 25 degrees inclusive angle with a Paper Wheel coated with 15 micron diamond compound, and finally removed the tiny burr with a second Paper Wheel coated with 0.25 micron diamond compound.

    This leaves the scratch pattern created by the 15 micron diamond particles intact as much as possible, creating an edge that with the naked eye almost looks like a mirror, but which has the bite of a coarser edge.

    I call this a "bling & bite" finish, and i have found it to work very well in EDC use on harder high carbide steel types.

    It's also quite difficult to show correctly in pictures, as the lens of my cheap camera has a tendency to show more of the scratch pattern than can be seen in reality with the naked eye.


    With the reduced edge angle & the much finer edge finish the knife will not only cut in a completely different league, it can now also be kept sharp on the 30 degrees slots of a Spyderco Sharpmaker or Lansky Turnbox.


    After sharpening:



    Specs:


    Length open: 22,2 cm

    Length closed: 12,7 cm

    Blade length: 9,6 cm

    Blade thickness: max 3,0 mm (ricasso)

    Edge length: 8,8 cm

    Steel: ZDP-189 powdered steel

    Hardness: 64-65 HRC

    Weight: 103 gram

    Handle material: British Racing Green FRN on steel liners

    Post from someone on Bladeforums:


    "According to CRK at the booth at Blade yesterday, Aceco does their heat treat.
    They have been running their blades 59-60 RC for about two years now (not sure of the exact date, maybe August 2013), they have just not updated their web site.
    If you look at the Inkosi it says 59-60, while all the others say 58-59.
    I noticed this and asked about it"

    Some time ago i did this rather large Strider fixed blade in S30V steel for a Dutch forum member.

    According to my Tormek angle gauge the factory edge measured 50 to 55 degrees inclusive and it wasn't very sharp either.


    Grit progression: reprofiled on a standard Paper Wheel with 220 grit SiC, refined it a little with a second Paper Wheel coated with 15 micron diamond compound, and finally removed the tiny burr with a third Paper Wheel coated with 0,25 micron diamond compound.

    The new & slightly convex edge measures around 35/36 degrees inclusive, and can both slice single layer toilet paper and treetop the hairs on the back of my hand.


    kwakster Sorry for that really stupid question... But what is Paperwheel sharpening? I really didn't heard that before... But I'm really interested because the edges look really nice!
    Regards


    Basic sharpening with a standard set of Paper Wheels is shown here:


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    I started sharpening with a set like this in 2009, bought from Armin Dobstetter from Custom Leather in Germany:


    http://customleather.ellvis.de/index.php?go=detail&ID=1001


    If you or anybody else has any questions about what you see here, fire away, :)

    A Chinese Ganzo 704 as i received it from Hong Kong:



    A very nice knife for the money (i paid about 17 US dollars including shipping from Hong Kong to the Netherlands), but with quite an obtuse edge angle of about 35-40 (ish) degrees inclusive and also a bit blunt not a very good cutter.

    On the blade it says 440C stainless steel, but it's more than likely it's Chinese cousin 9Cr13MoV.


    Reprofiled with a standard Paper Wheel with silicon carbide grit to 30 degrees inclusive, refined it just a bit with a second Paper Wheel coated with 15 micron diamond compound, and finally removed the tiny burr with a third Paper Wheel coated with 1 micron diamond compound.

    It cuts hair above the back of my hand and can slice single layer toilet paper.


    A while ago i reprofiled & sharpened this Ontario Afghan Bush in (probably) 5160 steel for a Dutch forum member, who when he received it tested it quite rigorously to see how the the knife would hold up with it's new edge.

    The pictures show the knife with it's new edge measuring 35 degrees inclusive, a 15 micron diamond compound Paper Wheel finish, and a treetopping sharpness.



    This was the mail i got from him when he was done testing:

    (translated from Dutch)


    Hereby i send you the results of the batonning test: my arm hurts and the knife just laughs at me.


    I started with batonning through some standard firewood, which didn't cause any problems.

    Then i proceeded to baton right through a hardwood pole with a big burl (?) in it (with a lot of effort from my side)

    I then replaced the baton with a hard rubber hammer for a bit more comfort and hitting power, and with this i managed to drive the edge about half an inch crossgrain into another piece of tropical hardwood.

    After this i cleaned the knife, and the edge would still pushcut through paper.


    I almost forgot to mention that i also put the knife sideways with the point on a wooden block and gave it about 20 hard whacks with the rubber hammer on both sides of the knife.

    Then i tested the point strength by stabbing it into hardwood and breaking it free sideways.

    I think the knife already has endured more than it will ever have to in real life.


    After all this i could still shave the hair on my leg on skin level, and after a bit of stropping it could treetop again.

    Since 2009 i've been sharpening knives on Paper Wheels, and i hope i'm not i'm the only one on this forum.

    From time to time i will post my results here and i hope that others will do the same, 8)


    Here's one i did a few days ago, a Spyderco Paramilitary 2 in Elmax steel.

    The factory edge had some light brown discoloration near the tip on one side, traces of some unknown black stuff that couldn't even be removed with acetone (visible in pic 1 & 3), and it could also barely cut copypaper.


    This is how it looked before sharpening:



    First i removed the apex of the old edge by cutting a few times in a silicon carbide stone, then resharpened it with a Paper Wheel coated with 15 micron diamond compound, followed by removing the tiny burr with a second Paper Wheel coated with 1 micron diamond compound.

    This time i also polished the bevels a bit more with the same Wheel, just to see how the Elmax would do.

    According to my Tormek angle gauge the new edge measures 30 degrees inclusive, can slice single ply toilet paper and easily whittle the hairs on the back of my hand from heel to tip.


    A guy over on British Blades had this to say about the material, and for the most part i tend to agree with him:


    "Cera Titan
    Now this is a weird material, its a Titanium composite with large quantities of carbides.
    As the Ti wears away during use the knife loses its shaving hair edge about as quickly as 440a/6a grade steel, thus not at all impressive.
    However, the edge left is a carbide chainsaw of cutting power !
    This knife looks and feels dull after a good work out at some cardboard boxes, yet still cuts like the Devil himself !
    I note the grind almost rounds the tip, suggesting that while this is much more flexible and tough than the ceramic models this is not a blade for cutting nails or dropping...
    In my opinion the better choice over ceramic blades.
    Much like Talonite, Dendrite cobalt alloys, only less expensive and probably a little tougher.
    I like this material and it will not rust, ever."


    IMO the knife is however much tougher than it looks & feels, and dropping it will definitely not result in breaking the blade (wife dropped it twice on hard laminate)
    If however it falls edge first on a tile floor i guess it could sustain a damaged edge, but given the relative flexibility of the blade i don't think it will be in the order of magnitude as could be the case with full ceramic blades or full hard Japanese kitchen knives in white or blue paper steels.
    The difference lies in that very resilient titanium matrix.


    Mine is still being used in the kitchen almost every day, and the edge is still sharp enough to slice tomatoes.
    Everyone who uses it here likes it for it's ultra-lightness, the fact that it's totally corrosion proof, and women especially like the fact that it looks harmless because of the short and bluntish santoku-shape.
    Sharpening to armhair shaving on skin level can be done with just silicon carbide, but for refining all those cubic boron nitride particles and vanadium carbides in the titanium you absolutely need fine diamond compounds and/or sprays.
    Doing this will reward you with a thinner apex that makes the knife cut even easier.