Quantcast

Cant keep a knife sharp?

Discussion in 'Non-Firearm Weapons' started by Axis II, Mar 13, 2018.

Thread Status:
Not open for further replies.
  1. Axis II

    Axis II Member

    Joined:
    Jul 2, 2015
    Messages:
    6,216
    Okay guys i don't know what the deal is but its driving me crazy!! I use a lansky for all my pocket knives and from the coarse stone to the yellow ultra fine stone i can get them to take the hair right of my arm but let me cut a piece or rope, box, even a freaking apple or two and the edge isn't there anymore. Is it because they are cheap knives?

    Gerber paraframe mini, a couple Kershaw's from the Wal-Mart case. I buy cheap knives cause I've broken tips, lost them.
     
  2. JeffG

    JeffG Member

    Joined:
    Jan 6, 2017
    Messages:
    1,724
    Location:
    NE Wisconsin
    Those knives are hard stainless steel. Sounds like the edge is rolling or there is a wire edge. Try a DMT diamond hone.
     
    Slamfire likes this.
  3. Axis II

    Axis II Member

    Joined:
    Jul 2, 2015
    Messages:
    6,216
    Could you explain what that does or why the edges might be that way? Would changing the angle be a good idea?
     
  4. Fiv3r

    Fiv3r Member

    Joined:
    Sep 30, 2009
    Messages:
    2,938
    One of the reasons I always recommend developing free hand sharpening as a skill is because it allows you to understand the basics of blade edges a bit better.

    Don't get me wrong, the Sharp Maker can get a blade sharp enough to whittle a gnat's hind quarters. However i still like to free hand.

    Jeff is probably onto something. My guess is a wired edge and/or a thicker grind.

    Steel that is honed can be left with a very thin edge that will readily take the hair off your arm. However, once it encounters material of any substance that site will roll over and deform.

    Check the edge carefully with your thumbnail to see if it fits or bites or drags. Carefully thumb the edge by running your thumb from the spine up to the edge flat along the broad of the blade. One side or the other may have a tiny wire folded down enough that you'll feel it drag on your skin.

    I'm a convex guy. I have been for over 15 years and it continues to be my go-to edge profile. So in your situation I would make sure the edge is nothing more than a floppy wire and not real damage or missharpened then strop the edge on a piece of loaded leather until you can no longer detect the site dragging.

    You'll probably be left with a more durable edge that will still take hair off your arm. The only draw back is that it's probably not going to shave the ink of newspaper (at least until you really get the convex thing down), but given the type of steel you are working with it shouldn't matter.

    Good luck:)
     
  5. ilbob

    ilbob Member

    Joined:
    Jun 14, 2006
    Messages:
    18,225
    Location:
    Illinois
    softer steels are much easier to sharpen but need more frequent sharpening. it is usually as simple as that.
     
  6. Axis II

    Axis II Member

    Joined:
    Jul 2, 2015
    Messages:
    6,216
    On the back edge of the blade there is a very slight burr.
     
  7. Fiv3r

    Fiv3r Member

    Joined:
    Sep 30, 2009
    Messages:
    2,938
    That's probably your performance hang up. Sharpening is cat-skinning territory. Everyone has their own way, and I don't think any of them are "wrong".

    If it were mine, I would strop it. A strop is easy to make. Any old piece of leather will do. If you want, you can load it with polishing compound. I usually use the paste they sell in the rotatory tool section at Lowes. It's cheap and last forever. It will polish the burr off in short order. Sometimes I cheat a bit and run the blade down a butcher steel a few times to weaken the wire edge before I strop it.

    Some guys use belts, some mouse pads. I just use a piece of 6oz leather I had left over from a project. Truth be told, cardboard or your pant legs will work in a pinch too;)
     
  8. NoirFan

    NoirFan Member

    Joined:
    Jul 25, 2006
    Messages:
    673
    When straightening out the burr, is there anything wrong with lightly dragging your blade backwards across the stone a few times on each edge? First I do the burr check with my thumbnail, then lightly pull the blade across the stone towards me.

    That's how I've always done my kitchen and pocket knives and it seems to work fine.
     
    JeffG likes this.
  9. Fiv3r

    Fiv3r Member

    Joined:
    Sep 30, 2009
    Messages:
    2,938
    I wouldn't think so. I'm not a sharpening guru,though. Someone with much more knowledge would be able to answer it better:D I would say that if the blade is sharp, it's sharp, right?:D
     
  10. JeffG

    JeffG Member

    Joined:
    Jan 6, 2017
    Messages:
    1,724
    Location:
    NE Wisconsin
    +1 I do free hand sharpening. I find that the harder steels aren't effectively cut by some abrasives. Back steeling or back sharpening is a good technique, but your abrasive has to be able to cut the knife steel. I use DMT hones, and touch up on a butcher's steel, that is paired with stainless steel. The hand me down steels are paired with old time carbon steel. The stainless knives will damage old steels.
     
  11. JeffG

    JeffG Member

    Joined:
    Jan 6, 2017
    Messages:
    1,724
    Location:
    NE Wisconsin
    A steeper grind might help.
     
  12. GLOOB

    GLOOB Member

    Joined:
    Sep 16, 2007
    Messages:
    5,955
    Everyone agrees what a bur is, more or less. It's a bit of excess, malleable metal hanging off the apex of your knife. This bur doesn't spring back. It stays where you push it.

    How and why it forms? i have my own ideas, but that's religion, and I'm not going to step into it.

    A simple way to detect a bur is to rub your finger over the SIDE of the knife, past the edge. Like stropping over your fingertips. First one side, then the other. If you have a bur, one side will be completely smooth, like your finger tip is just falling over the edge of a cliff. The other side will have some roughness/friction. If you feel it on one side, you should be able to take a pass on that side of the knife. And if you hit the apex, you should be able to now feel the burr on the other side of the knife. A very, very small bur is completely acceptable for anything but a razor, IMO. If very small, it will not really have enough length to roll far enough to cause a problem, and it will aid in slicing flesh and skin and rope and vegetable peels. In this case, you should be able to feel it, with experience, but it will be somewhat difficult to tell which direction it is going, and it won't change (much) depending on the last side you sharpened. But anything beyond a very tiny bur is generally undesirable for any knife.

    One of the simplest ways to remove or at least reduce a bur is to use a ceramic rod. One of the most sure and easy ways to completely remove a bur is with a strop loaded with compound. You can also remove a bur using regular sharpening stones, but it gets a bit more complicated than that. Specific brands come into play. And/or different strategy/preparation/use of the stone. Some advocate ripping the bur off by running the knife over the corner of a block of wood, and this works when the bur is pretty darn small. But again it depends. Strop and ceramic rod are pretty much foolproof.

    Steeper sharpening angle will help if your edge is rolling. But if it's just a bur, it won't change anything. The bur forms no matter what angle you sharpen at. Esp with a guided system like a Lansky using hard and flat stones. That said, one (of many) methods for removing a bur is to steepen the angle AFTER you're done sharpening, and use a fine stone at this steeper angle to cut the bur off with just a very light pass or 3. Some call this a "high pass." Some call it a microbevel. Some insist this is simply deburring and isn't creating a microbevel, at all. Again, I have my own opinion, but I'm not going to step into it.

    There are ways to reduce bur formation, in the first place. But, IMO, the important step for now is to learn how to detect it. And to learn at least one way to remove it.
     
    Last edited: Mar 13, 2018
  13. Axis II

    Axis II Member

    Joined:
    Jul 2, 2015
    Messages:
    6,216
    Now of I rub the edge to check sharpness and the front edge feels very smooth and not sharp and the back feels sharp and has the burr what would that mean?
     
  14. Fiv3r

    Fiv3r Member

    Joined:
    Sep 30, 2009
    Messages:
    2,938
    My guess is that your geometry is off a bit and you've formed a burr toward the bottom of your blade while under sharpening the front.

    Truth be told, I can't use a system to save my life. My layer father in law, God rest him, bought me a sharpening system for my birthday over a decade ago. I couldn't seem to get an edge with it as well as I could with an Arkasas stone and a strop.

    Keep in mind, I favor khukuris, and systems don't tend to work well on such exaggerated recurves.

    You might try your luck with a stone and see what happens. I find the easiest way to use a stone, an introductory way if you will, is to do circular passes over the edge going by feel.

    The late great Chuck Buck actually included a pamphlet on this method with the Buck 110 years ago.

    Is should yield a constant edge that you can refine more as your skill improves.
     
    Slamfire and Axis II like this.
  15. GLOOB

    GLOOB Member

    Joined:
    Sep 16, 2007
    Messages:
    5,955
    This means you have a big enough bur to cause the symptoms you originally posted. This is not a surprise, at all. Sharpening on flat, hard stones will always, 100% of the time IME, raise a significant bur. But just for your own understanding/experience, you might like to put the knife in your lansky clamp and using your finishing stone, sharpen one side, then the other, feeling for the bur. To see for yourself how the bur flops from one side to the other.

    Now you get to learn how to remove/reduce this bur. You can play around with your current equipment. You can try stropping on jeans. You can try a block of wood. You can try hopping around on a full moon and stropping across one of your lanksy stones backwards 3 times. You can try the high pass method (and decide for yourself if this leaves an edge good enough for your liking). But if all else fails, a leather strop loaded with chromium oxide (or an even coarser compound if you like) will be able to remove a bur in the hands of almost anyone. The chrome ox also is so fine that it almost always improves an edge. Everyone who gets into knife sharpening will at one point in time fall in love with the loaded strop like it's magic. But it's not the only way to get a clean and sharp edge.

    BTW, when you completely remove the burr, both sides of the knife will feel almost completely smooth (and thus "not sharp," by your reckoning). If you manage to create a tiny (conditionally useful) bur, the knife will "feel sharp" in both directions, no matter what side you sharpened last.
     
    Last edited: Mar 13, 2018
    bikerdoc likes this.
  16. GLOOB

    GLOOB Member

    Joined:
    Sep 16, 2007
    Messages:
    5,955
    OK, here are a variety of methods which people have come up with to remove a bur and which I know always work when performed correctly.

    1.High angle pass / microbevel. Already described.
    2. Plateau sharpening: This is where you say to heck with it. You rub the knife on the stone at 90 degrees in order to remove the bur. Then you sharpen it again but stop before the bur gets too big.
    3.Use friable/muddy stone. E.g. many Japanese waterstones fall into this category. The abrasive slurry tends to erase the bur. But too much of "a good thing" will also make your knife not as sharp. So you need to use the right stone/brand/model for your knife steel/bevel. But if you learn your stone, you can also control the amount of slurry by washing some of it off.
    4. Fine ceramic rod
    5. loaded strop

    4 and 5 can be used after your lansky sharpening, so you don't really need to change what you already know.
    1 and 2 can be learned on your lansky. But 1 requires a higher angle than you might like. IME, it takes at least 10 degrees higher than what you sharpened at, per side, when using non-slurrying stones. But it is somewhat dependent on the stones you are using. It could be higher. And it requires some finesse. And, well heck with it. To be honest, it does indeed create a microbevel, and my chisels will prove it quite easily. And 2 requires some plain old trial and error and really don't get the best sharpest edge, which even the proponents of this method will concede.

    4. ceramic rod is one way to get the "tiny/useful" bur. This type of sharp edge is very dangerous to handle, worse than a razor edge. It will open your skin up real easy, so be careful. Another way to get this type of action... well this is going to be controversial. You can round the surface of your lansky stones just slightly, side-to-side. But then you have to use them in a sweeping/drawing motion to keep your edges even. Again, this may be controversial, but IMO the reason the rod works is because it is not flat. So despite being hard and not having any abrasive slurry, the bur is limited. Hard + flat creates bur because there is no slurry, plus there is a large area of flat contact between the stone and the bevel. This makes for very little cutting and relatively higher burnishing. Burnishing is essentially a product of friction and it amounts to moving metal around on the surface of the steel without removing it. This is opposed to abrasion/cutting, which is actually producing a very tiny chip, which you can liken to the threads of steel sent off while drilling or milling. And burnishing is (IMO) one of the main factors in creating a bur on finer stones. Burnishing pushes metal without removing it. And pushing this crappy metal over the apex without removing it lines up with what a bur is, in my book. You can experiment with this yourself, maybe starting off with slightly rounding just the edges of your finer stones, and lightly angle the stone towards that rounded edge while drawing it across the blade.

    Also, if you are using water on a hard stone, this increases friction and increases burnishing. On hard stones, oil reduces bur formation. Again, my opinion, only. I don't want to ruffle feathers.
     
    Last edited: Mar 13, 2018
    Slamfire, JeffG and Axis II like this.
  17. JohnKSa

    JohnKSa Moderator Staff Member

    Joined:
    Jan 1, 2003
    Messages:
    16,599
    Location:
    DFW Area
    A burr will generally leave the blade shaving sharp when one side edge is against the skin but dull when the other side of the edge is against the skin. The burr is very thin and will catch and cut the hairs. But when you try to shave with the other side of the blade, the burr is going in the wrong direction and the blade will seem dull.

    When you're sharpening, you want to be sure to use progressively lighter pressure as you go through the process. For the coarser stones, you can press harder initially, getting lighter as you get close to being done with the stone. By the time you're using the fine stones, the pressure should be very light, even when you first start using the stone. Pressing with any force on a nearly finished edge with a fine stone will bend it over and cause a burr.

    Once you get a burr-free edge that is sharp, if it doesn't stay sharp through reasonable cutting tasks, then you need to go to a larger edge angle to make a sturdier edge.
     
    bikerdoc, JeffG and Axis II like this.
  18. Axis II

    Axis II Member

    Joined:
    Jul 2, 2015
    Messages:
    6,216
    Well I got the lansky pedestal tonight and started over with a steeper degree seeing how its more a utility knife and I now do NOT have the burr on one side and not the other. Both sides feel extremely sharp and shaved my arm hair. I will report back with how sharp it stays but this feels a lot different than before. This time both sides feel sharp.
     
    JeffG likes this.
  19. Axis II

    Axis II Member

    Joined:
    Jul 2, 2015
    Messages:
    6,216
    I tried using different pressure and also a steeper angle and it seems to feel better than before. The edge is smooth but both sides feel sharp and not just one side like before. I used some pressure with the course stones and lightened up to no pressure at all with the extra fine stone.
     
    JeffG likes this.
  20. Axis II

    Axis II Member

    Joined:
    Jul 2, 2015
    Messages:
    6,216
    Got another question for you guys.

    Lansky offers their sapphire stone which is supposed to be better than extra fine and also a strop. If I strop with an old belt do I need to "maintain" the angle or would I be better suited by the Lansky strop? Right now I can shave my arm with the extra fine stone.
     
  21. JohnKSa

    JohnKSa Moderator Staff Member

    Joined:
    Jan 1, 2003
    Messages:
    16,599
    Location:
    DFW Area
    Sapphire is usually sold as ceramic or as aluminum oxide--all the same thing. If you want to put a really fine edge on a knife, you can finish it off by polishing it with a very fine ceramic stone or a strop.

    If you use a fine ceramic, the pressure should be light--almost just the weight of the stone--and it's very important to keep the angle very consistent. That should be easy with a lansky system.

    If you're working freehand, it might be easier to put the final touches on an edge with a strop. That's becasue the angle isn't real critical on a strop. What you don't want to do on a soft/compressible strop is to press hard enough to compress the strop material significantly.

    If it's shaving sharp and will maintain the edge after reasonable cutting tasks then you're probably already in good shape.
     
    Axis II and Fiv3r like this.
  22. Fiv3r

    Fiv3r Member

    Joined:
    Sep 30, 2009
    Messages:
    2,938
    I have found that you get diminishing returns the more you chase "sharp" down the rabbit hole.

    I can see a specialized knife like a scalpel for brain surgery being ridiculously sharp. However, my personal threshold is hair popping sharp that will stand up to a day's work.

    Generally, unless I am cutting abrasive material all day, a routine wipedown of the blade and a maintenance strop will keep my knife very sharp for a long time.

    I probably hone/reprofile my using blades 2-3 times a year. Stitch in time stropping seem a to keep the edge serviceable.
     
    Axis II likes this.
  23. Axis II

    Axis II Member

    Joined:
    Jul 2, 2015
    Messages:
    6,216
    I currently finish with the yellow ultra fine stone. Its a very smooth white surface. Is this good enough or should i get the finer stone? It used to take the hair off my arm but after cutting a few apples and a piece of rope i couldn't even get it to cut paper. I switched to 30 degree last night for a steeper edge and it will take hair off my arm but time will tell how it maintains the sharpness.
     
  24. Axis II

    Axis II Member

    Joined:
    Jul 2, 2015
    Messages:
    6,216
    Just looking for it to stay sharp rather than razor sharp. I could cut a piece of paper cleanly with it but after cutting a few things like a box, 3-4 apples and a piece or rope like Para cord i would be lucky if it would cut my finger if i ran it over it.
     
  25. JohnKSa

    JohnKSa Moderator Staff Member

    Joined:
    Jan 1, 2003
    Messages:
    16,599
    Location:
    DFW Area
    Unless you're cutting the apples against a glass cutting board or something similar, that shouldn't dull the knife at all. And one piece of rope shouldn't do anything significant either.

    I'm beginning to think that the steel on that knife is very soft. Either that or you're still getting a wire edge that is rolling over as soon as you use it just a little bit.

    When you're using the lansky system, make sure that the stone is moving towards the edge of the blade during the sharpening process--as if the knife is carving the stone. That should help a little with preventing a wire edge. Sometimes if I have a knife that is really prone to getting a wire edge, I will finish up with one very light pass over each side of the edge with a coarser stone to pull off any wire edge that may have formed--again, moving the stone toward the knife edge as if carving the stone with the knife.

    One other thing that can be important is that I find it important to alternate strokes on the knife, especially toward the very end of the sharpening process, turning the knife over so that the stone alternates sides on the edge with each stroke. This also helps prevent a wire edge.
     
Thread Status:
Not open for further replies.
  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice