Sharpening with Belts

Discussion in 'Knife Maker Shop Talk' started by Mike Martinez, Sep 26, 2012.

  1. Mike Martinez

    Mike Martinez Well-Known Member

    I've been sharpening with stones for years and generally avoid using belts for anything other than setting the primary bevel with a 120 grit ceramic. So, my question is, what type of belts do you use in your like up and are there any tips and tricks to it? I'd continue to hand sharpen everything but the volume of knives of knives is steadily increasing so I need to find a better way. I'll probably continue to finish by hand but would like to get 95% of it done.
  2. SBuzek

    SBuzek Well-Known Member

    I use a worn 400 grit then a 30 micron then 15 micron,hard buff with green chrome and then strop.

  3. J.Babody

    J.Babody Member

    I also decided to give this a shot on my little 1x30 harbor freight special. I bought a succession of belts up to 9 micron, specifically some norax pyramids and some gators, and than a couple leather belts from usaknifemaker. I have yet to try it because a skunk took up residence in my garage so I can't say how it performs yet. But I do all reshaping and sharpening by hand so I can't wait.
    I'll let you know how it goes as soon as I get a chance to try it, but always remember to keep dunking that blade constantly. Fast to sharpen, fast to ruin a blade...
  4. rhinoknives

    rhinoknives Well-Known Member

    I have been doing almost all of my sharpening for customers on my 2 x 72" Variable speed.
    I like to run at about 25-30% speed tops to help keep things cool.

    I use Hermes superflex in 120 Then 600 and stop and buff with Green chrome for German & Americana type culinary knives.
    Then for Japanese a go from the 600G to 3M 15 Micron then 9, Appox/2000 Grit and then a buff with green chrome.
    Also the buff is more of a Burnishing with a far amount of pressure.

    This works great to achieve a strong and sharp convexed edge.

  5. Doug Lester

    Doug Lester Well-Known Member

    It is also going to depend on what you are doing with the knife. My chopper that I use for brush clearing is sharpened on my grinder with 220 grit. My kitchen knifes are sharpened on a crockery stick sharpener. My pocket knife or anything that I want a finer edge on are sharpened on stones and stropped on leather.

  6. Mike Martinez

    Mike Martinez Well-Known Member

    Thanks guys. I have quite a bit of experience sharpening different blades on stones so my technique is set for better or worse. This experience is limited to stones as when the knife bug bit, I spent a few thousand buying high end natural stones and synthetics of the same repute. I've since cut back and left only the stones that work for me and my style so finishing edges isn't much of an issue. The only thing I'm a bit new to is sharpening with belts. I've done a few knives on a small taut slack portion of belt and am ok with them (choppers), now I've started to experiment with refining edges a bit farther on the grinder (variable speed) so that I can jump over to the 6K-30k synthetics and then hit the felt and leather. The only big issue I've had is getting a FLAT edge off belts. After grinding, they look fine but when they hit the stones, you can see that they are anything but. It may be worth mentioning that I flatten every stone prior to sharpening and check them during sharping. It may sound nuts to take and edge into the 6k-30k range especially when the edge degrades down to a 1K-5K after a few cuts but I do love a scary sharp edge. And I've noticed that a straight-razor like edge is almost always welcomed by potential owners.

    Anyhow, I'm rambling. You guys have given some good advice here and it will be used when ordering from Super Grit tonight.
  7. Doug Lester

    Doug Lester Well-Known Member

    I'm not sure that I understand what's happening. If you are using a slack belt to sharpen with you will not get a flat secondary bevel. If you are using your platen then I would say that you are not holding a constant angle when you make your passes.

  8. Fred Rowe

    Fred Rowe Well-Known Member

    Belts don't give a truly flat surface, neither on bevel or edge. I think thats why it shows when you use your stones. Try it on a disc and you will notice the difference.

  9. Mike Martinez

    Mike Martinez Well-Known Member

    Doug, sorry for the incoherent rambling, chalk it up to too much caffeine and not enough sleep. Anyhow, I flatten my stones using a reference granite plate so they are flat as one can get them in a shop setting (.002) and no matter how flat they are coming off of the belts, they don't compare to them coming off the stones. Though this is the case, they'll flatten out quickly on an 5k stone coming off of a 220 to 400 grit worn belt. I'd like to incorporate a better belt repertoire to my routine. They come off nearly flat off a lower grit so I figure that a higher grit would allow the edge to be even closer, though I may be mistaken.

    Thank you Fred, I've noted how not flat things are off of a belt even with a great platen. I have a few disc sanders but I've never attempted to sharpen with them. It might be worth a try once I get a beveled disc again. I needed some other tools and sold my least used grinder... sadly that happened to be the one I need most now.

    Well Gents, thanks again for your help. I know that it seems a bit petty and obsessive to chase and edge with more devotion than I do my overall grinding but an ugly knife with a good sharp edge is millions of times better than its opposite. :biggrin:
  10. rhinoknives

    rhinoknives Well-Known Member

    Stiffer belts give a flatter edge if you want it?
    In my Less than Humble opinion, Convex edges "done right" cut better and last longer that a truly flat edge.

    It's called sectional density I believe? More metal behind the cutting edge.

  11. Doug Lester

    Doug Lester Well-Known Member

    Yer an honest man there, Lawrence. Can't say that I believe much in humble opinions myself, especially when someone says it's a humble opinion.

  12. rhinoknives

    rhinoknives Well-Known Member

    I didn't ask you what you believe in and you are on the way to getting another thread closed.

  13. Frank Niro

    Frank Niro KNIFE MAKER

    Well, I sharpen to get a "pumkin seed" edge. This tio me is the ideal edge that has support. I do this on the slack belt section of my 2X72. I start with 120, do 220, do 400, do 30 and then go to a soft buff with green rouge. I do not have a reversing machine so I hold the blade edge down in the same direction the belt is turning. Frank
  14. rhinoknives

    rhinoknives Well-Known Member

    Forget to mention that I use a slack belt with the edge up into the belt to achieve the Convex or Pumpkin seed edge that Frank is referring to. "Halloween is near!"

    Also some days I sharpen up to about a 100 knives. So it makes much more sense to have the abrasive do the moving than the knife.

    Many different techniques should work? It's the results we are after.

  15. Josh Dabney

    Josh Dabney Moderator


    Everything in knifemaking is a compromise !

    A covex edge and stones work fine together as long as the covex is at a shallower angle than your sharpening angle. In this scenario you'll have a convex with a micro-bevel as your sharpening bevel. This is what I do and like it fine. It's convexed for support behind the sharpening bevel and quick and easy to sharpen on stones due to the extremely small amount of steel that needs to be removed on the micro-bevel to resharpen.

    A true convex like Frank does is great but will have a micro-bevel as soon as it hit's a stone anyway. A belt or mouspad sharpening will keep it a true convex when sharpened but who does that ??? besides us crazy knifemakers ?

    A few factors will effect how flat that sharpening bevel is off a slack belt-
    1. how sharp is the belt doing the cutting
    2. how much belt tension
    3. how much pressure is applied against the belt while cutting in the edge

    when using the grinder to sharpen I use the slack section between the platen and top wheel on my KMG with the tension extremely tight and light passes to get the sharpening bevel to keep it flat as possible. This will give a FAR different result than doing it in-between the wheels on a slack belt with low tension and no platen.

    IMHO your shooting for a unicorn IF you want to finish on those high grit naturals. With your goals I'd cut to a burr on a 220 then refine that with a wore 400 then go to the stones. Either that or do it all with belts like these fellas suggest.

    Flatening an edge with a 6k just doesn't sound like fun to me and I like to hand sharpen, ;)

    I'd feel MUCH better starting with a 600 grit stone or my newish 725 grit diamond stone to end up with your natural stones.

    Take care man !

  16. Fred Rowe

    Fred Rowe Well-Known Member

    Not all blades are created equal. Some blades cannot be made sharp. Either the geometry of the bevels is poorly thought out. The grinds themselves were poorly executed. The bevels were not taken to completion.The steel the blade is made from does not have good sharpening characteristics. If there is nothing to start with, you will end up with little at the edge. Its easier to apply a convex edge to a blade than a flat one. There is little to indicate that the convex edge is superior to the flat ground edge. Arguing there is more material behind the edge is a little miss leading. We are not talking in terms of feet and inches; we are talking about thousands of an inch. There is little difference in flat or convex over so small an distance.
    Before you begin, take a good look at the blade you are sharpening and see what the possibilities are. I use many different techniques to sharpen depending on the blade that I'm working with.
    Have a good one, Fred
  17. rhinoknives

    rhinoknives Well-Known Member

    Pardon Fred,
    It is because we are dealing with a small area that a Convex / Appleseed edge gives a superior cutting edge.

    A favorite of Bill Moran, Ed Fowler & Wayne Goddard Just to mention a few of the fathers & Greats of modern knife making.

    There is a increase in strength & longevity of the cutting edge,also you can cut circles with less resistance. Hunting/Boning knife edges benefit greatly from Convexing.

    I sharpen for many Chef's & Butchers/Meat cutters here in L.A. and they all reported a increase in sharpness & longevity as well as my own findings with my own knives.

    Try it! You will like it!

  18. Fred Rowe

    Fred Rowe Well-Known Member

    I get excellent results with a convex grind, if I were to grind identical blades, one with a convex edge the other flat ground, both with the same angle along the chord, the convex would be heavier by a minute amount behind the edge. With the flat grind, same angle, the edge tends to disappear, it gets ground away. The infinity effect. If I made cuts with both blades right after sharpening the flat ground blade would make the better cut. Its thinner. The convex would last longer. Its in the math. I would not agree that a convex edge is the best grind in every situation. That decision should take into account the degree of hardness and ductility of the edge along with the properties of the steel being used. My competition knife looks nothing like my counter ware. This is true with the primary bevels themselves but with less telling effect. Convex bevels on a competition knife makes seance to me, but not on a tool meant to shave. Different task. Of course its all about performance in the end and if how you grind edges is giving your customers the results they are looking for then you are doing it the right way.
  19. rhinoknives

    rhinoknives Well-Known Member

    I agree that one thing is never good for everything and a convex probably wouldn't work well for a razor?

  20. Fred Rowe

    Fred Rowe Well-Known Member

    I figure you take all aspects of a blade, you are about to sharpen, into account as second nature being in the sharpening business.
    For newer makers that visit these threads, I want them to go away with a broad view of the many aspects of making a quality knife blade. I don't want them to think any one process or approach is a panacea, which will bring them success, while disregarding many of the basics. As you well know there is a lifetime of knowledge embodied in any accomplished knife maker.
    Regards, Fred

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