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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.
     

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