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Convex Sharpening

Discussion in 'Sharpening' started by logan_lamothe, Aug 4, 2010.

  1. logan_lamothe

    logan_lamothe New Member

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    I have been trying to put a convex edge on on some of my Buck knives but all I seem to be doing is wearing out sand paper. Is there an easy way to do this or should I have a pro do it for me?
     
  2. Mythtaken

    Mythtaken Staff Member CKM Staff

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    Are you using a mousepad or something similar?
     
  3. logan_lamothe

    logan_lamothe New Member

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    MOuse pad with 3m sandpaper, 220,400, and 600 grit
     
  4. Mythtaken

    Mythtaken Staff Member CKM Staff

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    Unless the blade is really dull I wouldn't go below 400. It might take a little longer, but you don't run the risk of overdoing it and end up dulling the blade.

    Also hold the blade at a really low angle, almost flat down, really, and draw away from the edge. Keep the angle consistent all through the draw. You should start to see that wiry build-up on the edge. When you've done both sides, use a leather strop or steel to knock the buildup off the edge. Don't overdo it.

    I have heard that sometimes the steel is just too hard to take an edge this way. If that's the case for you and your Bucks, you might want to start off with a stone and put a good V edge on it, then use compound on a strop or some really fine sand paper to take the shoulder off it.

    Personally, I use a Sharpmaker. I find if I let my wrist roll a little when I'm using the flat side of the stones I get a pretty decent convex.
     
  5. logan_lamothe

    logan_lamothe New Member

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    I picked up a belt sander, now I need to go to lee valley for belts. Last weekend I found my self wandering through the farm yard trying to decide which leaf sprig I am going to pull off to make my first knife.
     
  6. Mythtaken

    Mythtaken Staff Member CKM Staff

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    What sort of grinder did you get?

    I recommend you look for ceramic belts. They cost a little more, but I tried some out a while back and I'm sold. They last twice as long as others I've used, run cooler, and can sure take off some metal.
     
  7. logan_lamothe

    logan_lamothe New Member

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    I just picked up a Master Craft from Canadian Tire for now. Where do you get your belts the only fine grits I can find are at Lee Valley?
     
  8. Mythtaken

    Mythtaken Staff Member CKM Staff

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    Those little disc/belt sanders are great for handle material, but I think you might be disappointed if you use it with blade steel. They just don't have the power or torque.

    For knife grinding you really need a 1 or 2hp grinder running 2x72 belts. There are a number of ready-made ones like Coote, Bee, Bader, Burr King, KMG, etc. Or you can have a go at making your own. There are a variety of plans floating around online. I know at least a couple of members here have or are in the process of building their own. Once folks get back into routine after summer, they should be around to give more detail.

    I use a 8" 1hp variable speed Bee. I chose it because I like the design and because it's Canadian. I love it. I get my belts from Rob at Canadian Knifemaker Supply (http://www.knifemaker.ca).

    Keep in mind that a belt grinder is a great tool, but you can get along without it. A good set of files will make a knife just as nice as a grinder. I still use files for a lot of my work. I mostly use the grinder for the bevels. It takes longer but you have very fine control.
     
  9. Mythtaken

    Mythtaken Staff Member CKM Staff

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    Just an update on the convex sharpening discussion...

    Yesterday I noticed it was time for a sharpen on a lockback I made some time ago. Rather than reach for the Sharpmaker, I dug out my imitation Hoodoo Hone (Just a block of wood with some mousepad on one side and some leather on the other, with slots cut in the end to hold the sand paper.) I stuck a piece of 1500 on it and gave the blade about 30 light strokes on each side. That brought it up to shaving sharp.
     
  10. NuViking

    NuViking New Member

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    My biggest problem wiht a good 2x72 is price...If one is a machinest you can make your own as I have witnesed. If you are using a 1x30 or 1x42 you will develop patience and consder making smaller knives....
    You mentioned using a leafspring,,Do you have a forge or access to a forge??
    Before sanding a leaf spring that is hardened or not annealed you will go though a lot of sanding and not get very far. If you do have access to a forge,,consider neotribal knifemaking. I have found that its very rewarding doing most of the work by your own hands and elbo greese. One problem I have found with leafsprings is they work great for making smaller blade knives. One problem I have found with springsteel and longer blades is that when you go to harden them they have a tendancy of going back to their original curve.
     
  11. NuViking

    NuViking New Member

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    Personaly I prefer coil springs. I fogre with teh coil instead of against it and have hade very little trouble with warping. We can get into testing potential steel in a future article if your interested. For now you may want to stick with a nice carbon steel like 5160 or O1.
    Try making blades that are about 2 to 2 1/2 inchs long with your belt sander,,,any longer than that is hard to keep a flat grind with a narrow belt.
    Another consderation wiht a small belt sander is scandinavain grinds,,,They have become my new personal favorite grind and are easy to maintain in the field or at work.
     
  12. Wishalot

    Wishalot New Member

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    Kicking in again to an old topic re: sharpening these Buck knives. I proudly own a 110 folder of 1960's vintage and I have to not so proudly state, I have never been able to get a razor edge on it. I got it useably sharp and kept it that way during one Season with a Gerber steel, however every effort I made to get it razor sharp just seemed to make it worse. It has been my Achilles heel of sharpening knives. Thank you for the information included herein - I may dig it out once again and give it another try.
     
  13. dancom

    dancom Dust Maker Best Shop Tool

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    I don't know what steel Buck 110 knives are made of, but I have encountered some knives that are frustratingly impossible to satisfactorily hone the edge. One was a diver's knife and would always leave a burr. Even stropping it would form a burr. Almost like tiny flakes or strands of chromium. I gave it back to the owner and never charged him. Another was a paring knife of unknown manufacturer that was a horrible thing. Not matter what I did and how delicate I was with the strop it wouldn't get very sharp. Aside from technique, which I hope I have down by now, the steel and heat treatment are critical. I have found that any knife made of good steel and well heat treated is a snap to hone up.
     
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  14. Wishalot

    Wishalot New Member

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    My experience level when first obtaining that Buck 110 was not high, so I just put it down to that as a cause, but, as the years rolled by, it became a total exercise in frustration and still is. No problem with any other knife of reasonable quality. People raved about this Buck 110 and I wanted so bad to appreciate it the same way the others have talked about it but I sure didn't appreciate it and still don't - the reason I have not and likely won't ever have another Buck knife. In short, I agree with your statement "any knife made of good steel and well heat treated is a snap to hone up". I should state in keeping with the topic of this post that the blade of my 110 is hollow ground with a convex edge.
     
  15. dancom

    dancom Dust Maker Best Shop Tool

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    The 110 appears to be hollow ground with flat cutting edge. The angle of the cutting edge looks to be about 20°(a guess), which is good for a general use. There should be a distinct cutting edge bevel of about a millimetre high. A primary only convex will be too fragile. Some straight razors have geometry like this. If you have a rig like an Edge Pro or Lansky, you can check the angle of the cutting edge by putting some permanent marker on it and adjusting the angle until the stone cleanly takes the ink off only the cutting edge bevel. Once the edge is good you can strop it and see how it comes up. My last few strokes on the strop are essentially the weight of the knife alone with no pressure. This should produce a very sharp edge. Like a brand new x-acto blade. If you can't get there, I'd blame the steel. Hahaha!
     
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  16. Wishalot

    Wishalot New Member

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    Well, now you have done it. A check of that bevel with the marker might just do the trick along with your other info. and advice. I will just have to give it another go now. I have a feeling I was concentrating too much on the slope of the hollow grind and not the actual bevel. I will update further. Thanks, Dancom.
     
  17. dancom

    dancom Dust Maker Best Shop Tool

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    Not a problem. Call me Dan. :)
     
  18. Griff

    Griff Active Member

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    I hope to tackle the ‘Convex’ sharpening dilemma by using the ability of my new grinder to run in reverse on the 2 axis tracking setup (adjusting the axis means the belts will not slip off) and combining that with my rotary platen. Those not familiar with the platen there’s a pic below, you can adjust the belt tension, and it’s used to convex everything from bevels to handles!

    [​IMG]
     
  19. dancom

    dancom Dust Maker Best Shop Tool

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    I've always wanted a rotary platen. I'd like a 4", 3" and 2" wheel to form a range of radii. Is your unit from Nexus?

    Dan
     
  20. Wishalot

    Wishalot New Member

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    Dan. Wonder of wonders - that 1 mm you referred to put my mind to work and with that marker and the change in angle, grades of sandpaper, 400 through 2500m, then stropping with green valve compound, lighter and lighter, I now have a Buck 110 turning pieces of paper into featherstick type formations. I guess the steel is fine - the user just learned a valuable lesson. Many thanks.

    Frank
     
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