flat grind to convex edge

Discussion in 'General Knife Discussion' started by jdc215, Mar 18, 2011.

  1. jdc215


    Mar 18, 2011
    i am new to this site this is my first post. i have owned lots of knives over the years but i have recently got the "seriously sharp" bug you could say. everyone i have talked to and everything i have read says that a convex edge is the best way to get there. my problem is that most knives from the factory are flat grind. how can a flat grind knife be changed to a convex edge?
  2. Jason B.

    Jason B. KnifeMaker / Craftsman / Service Provider Knifemaker / Craftsman / Service Provider

    Jun 13, 2007
    A convex does not make a edge sharper.

    A convex edge may be easier to get sharp because you can be sloppy without much negative effect on the edge.

    If most of your knives are V grind then stick with it until you figure out how to properly sharpen. Trying a new method takes more learning, continuing to try something new because your not getting the results expected only sets you further back.
  3. Mad_Maxx


    Nov 29, 2007
    to convex an edge, use some leather and sandpaper, sharpen "backwards"

    I convex most of my V blades, and when I sharpen I do convex going backwards with the knife


    a convex edge cuts easier than a V usually (hand sharpened)

  4. HandofCod


    Feb 27, 2010
    I reprofiled my recon scout to convex edge with pretty good results considering the tools are my disposal and my skill level. Just need some patience and a whole lotta sandpaper.
  5. richard j

    richard j

    Apr 1, 2007
    you can change a flat grind to a convex easily with a phone book and some sandpaper. if you want some help i would be glad to give you a call and talk youi through convexing your knives. its not really that hard to do with some instructions. [email protected]
  6. 40Degrees

    40Degrees Banned BANNED

    Mar 16, 2011
    practice with a cheaper blade

  7. marcinek


    Jan 9, 2007
    That is an excellent point that isn't made enough, I think. :thumbup: Well put.
  8. sherlockbonez


    Apr 28, 2002
    I've put a convex edge on a saber grind. Very easy to maintain and do not regret doing it.
  9. me2


    Oct 11, 2003
    You can put a convex edge on any knife, from hollow ground to full flat. A full convex grind is another thing. Full convex grinds are difficult to do on previously existing flat or hollow ground blades. I have been using flat and convex edges interchangably for years now and have not noticed any difference.
  10. Joshua J.

    Joshua J.

    Feb 27, 2005
    The grind type has almost nothing to do with sharpness. You can grind any blade to have a super thick edge that won't cut a thing.
    Oppositely you can grind any edge super thin, and it will cut like a laser. If the blade is too thick overall you'll end up re-profiling the entire thing just to get the right edge angle, so don't start with a blade that looks like a pry-bar.

    At the same time, I have seen some pretty thick edges shave pretty nicely, so it's not like you have to have a thin edge for a knife to be sharp. A thin edge will cut better overall though, and will keep cutting longer (when well cared for).

    The angle you use on an edge should be determined by your intended use for the knife. If you're sharpening a machete (or your relative's kitchen knives), chances are you'll want a relatively thick edge, because it will resist damage better when you accidentally hit a rock in the ground (or they try to chop through frozen meat with bones in it:mad:).
    If you are sharpening a small knife, I find it best to go as thin as possible, since these knives probably won't be hitting rocks any time soon, and the extra cutting ability in a small package is very appealing.
    To fine tune the edge, I like to grind it to an angle that is probably too thin, and then see if it rolls or chips during regular use. If it does, then you just apply a micro bevel. That is, make a few swipes on your finest grit sharpener at a slightly steeper angle than what you originally put on the knife. For example, I like to sharpen my knives at around 10-15 degrees overall (very thin, sometimes flat with the blade grind) and then put a 20 degree micro bevel on the edge.
    This way the very edge is more durable, but you keep much of the cutting ability from the thinner edge grind.

    To get a thick edge sharp it just needs a lot of polish, that's probably where the sandpaper tricks will come in handy the most.

    I sharpen on benchstones, so most of my edges end up somewhat convex. It seems that robots grind flat edges much better than I can.
  11. jdc215


    Mar 18, 2011
    from what i understand a convex edge is slightly easier to take care of and i find that appealing, i also am under the impression that it is easier to keep sharp once you get it sharp because it is easier to maintain. maybe im barking up the wrong tree all together. my issue arrises in that i recently baught some nice knives that came very sharp but iahve realized that i dont use them because i know that once they get dull i dont know how to get them as sharp as they are again. my thought with the convex edge is mostly centered around a hunting knife i have that looks real traditional and i just think it would look better with a convex edge and i would like it to be sharper for dressing animals.
  12. me2


    Oct 11, 2003
    I have not found convex edges any easier to take care of than any other type of edge. Maintaining a sharp edge is no easier or more difficult either IME. I do like convex edges for their appearance, which sounds like what you want for your hunting knife. There is a lot of hype about convex edges floating around, and it's difficult to tell what's what.

    I sounds like you just need to learn to sharpen your knives. Convex edges won't be any sharper than V edges. In the end, sharpening is all about proper removal of metal. Do you have any sharpening equipment and some cheap knives to practice on? Understand that convexing an edge will get it sharp, but it's not any easier or harder than a V edge. Also realize that if you sharpen without a guided system like an Edge Pro or Lansky, you'll end up with some degree of convexity just from the slight differences in your hands during the sharpening motion.
  13. elkpro1


    Jul 24, 2008
    The convex edge I put on freehand with a flat Diamond on a flat grind knife is the best way i know to keep any knife easy to maintain in the field .
  14. jeffa


    Jun 10, 1999
    One more advantage to a full convex edge is that when splitting wood it acts like a wedge the sharp edge initiating the cut and the wider/thicker portion of the blad forces the wood apart like a wedge. If the blade tip to shoulder proportion is correct the blade will continue to initiate the cut followed by the wedge action of the blade.

    It is far from my best skinning knife, I like a full flat grind and a thinner blade for that.
  15. Big Mike

    Big Mike

    Aug 30, 2006

    My best skinning knives have high hollow grinds and convex edges. :cool:

    Big Mike
  16. jdc215


    Mar 18, 2011
    to do that to my hunting knife would require extensive reprofiling i would be content i with just a basic convex edge to get rid of some of the hard lines and i think it i like the idea of stroping the blade when it gets dull rather than running one of those unholly carbide drag sharpeners over the blade.
  17. richard j

    richard j

    Apr 1, 2007
    :eek: please dont tell us that you use one of thoes pull through sharpeners.
    they are the worst thing you can use on a knife.
  18. jdc215


    Mar 18, 2011
    i have learned the folly of my younger years. Although tough to embrace, i have learned that patience is the key to good sharpening.
  19. somber

    somber Gold Member Gold Member

    Nov 9, 2009
  20. Joshua J.

    Joshua J.

    Feb 27, 2005
    That's pretty hilarious.

    He describes in six minutes what took me the last 5 years to figure out.

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