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Thread: Stu - Convex Grind?

  1. #1
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    Stu - Convex Grind?

    Stu,

    Just thinking out loud here, but I just got one of those little HF 1x30 belt grinder for doing knife sharpening. In another post you suggested I could use it for Lathe tools.

    That got me to thinking. (I know, a dangerous thing), but one of the things they talk about with knives and belt sanders is the ability to do a convex grind on it for knives.

    On my first try with an old camping axe I have, without hardly trying, I noticed that it had a convex grind. The belt gives just enough that it gives a nice convex shape. The added bonus is that with the give, I find it much easier to get a uniform edge along the edge of the tool.

    So, I'm just thinking this could be a great way of getting razor sharp skews with a convex grind, or do you think I'm missing something?

    Would there be any advantage to having a convex grind on say a roughing or bowl gouge?
    Programmer - An organism that turns coffee into software.
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  2. #2
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    The convex grind I've shown on the skew is just for the skew, well the parting tool as well, but for a bowl gouge, you want a flat grind, not a convex grind.

    That said, I know that a number of top turners advocate using a belt grinder compared to a stone grinder for their turning tools for a number of reasons, one of the biggest is that because of the length of the belt, it is much harder for the tool to get "Hot", as the belt is a much cooler system for grinding

    Cheers!
    The pessimist complains about the wind; the optimist expects it to change; the realist adjusts the sails.
    William Arthur Ward

  3. #3
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    A bowl gouge, specifically for hollowing, BEGS for a convex grind. I've been advocating that grind for years. Lots of folks use the fingernail grind, though, and that's really hard to make convex.

    A roughing gouge really wants a flat or very slightly concave (as on an 8" or larger wheel) bevel, though, as does a bowl gouge used for "outside" work.
    -- Tim --

  4. #4
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    Played around with sharpening one of my cheapy HF Skews today on the belt sander. Nice convex grind, sharp enough to scrape (I wont say it sliced them off exactly) hairs off my forearm.

    That's with a 120 grit belt and some of that green polishing compound.

    Can't wait till the finer grit belts and the leather belt from LeeValley get here.

    And no, I didn't get to try it on the lathe. Too many other projects piled in from of it right now...

    Click image for larger version. 

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    Programmer - An organism that turns coffee into software.
    If all your friends are exactly like you, What an un-interesting life it must be.
    "A door is what a dog is perpetually on the wrong side of" Ogden Nash


  5. #5
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    Looks good Brent, but I think it should be straight across the top cutting edge, not curved, like it looks to be (could be the picture).
    The pessimist complains about the wind; the optimist expects it to change; the realist adjusts the sails.
    William Arthur Ward

  6. #6
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    I think the curved edge is what he was shooting for - it helps to keep that tip out of the work... or so it's said. I've never tried a curved skew so I can't say whether it makes a difference.

    Seems like a convex bevel on a skew might be counterproductive - not much bevel to ride. It might work OK, though. One way to find out...
    -- Tim --

  7. #7
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    Tim, my large 1 1/4" skew is has the lower part of the skew slightly curved, but the top part, leading to the long point is straight.

    I think you will find that the convex grind on the skew work really well.

    Brent, having the skew curved to the long point is a bad idea, when you go to use the long point, the point you want to use will be behind the curved portion, not good.

    Try it again and make it strait across, well at at 15 degree bevel, but straight.

    Cheers!
    The pessimist complains about the wind; the optimist expects it to change; the realist adjusts the sails.
    William Arthur Ward

  8. #8
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    Interesting. I've got other skews that are straight across. This is just a cheap HF skew that I use for sharpening practice, basically.

    The curve on the skew came from somewhere on the interwebs. If I recall, it was supposed to reduce the likely hood of a catch.
    Programmer - An organism that turns coffee into software.
    If all your friends are exactly like you, What an un-interesting life it must be.
    "A door is what a dog is perpetually on the wrong side of" Ogden Nash


  9. #9
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    Quote Originally Posted by Brent Dowell View Post
    Interesting. I've got other skews that are straight across. This is just a cheap HF skew that I use for sharpening practice, basically.

    The curve on the skew came from somewhere on the interwebs. If I recall, it was supposed to reduce the likely hood of a catch.
    Yes, if the curve is on the bottom half of the skew, from just shy of the middle to the short point, but NOT from the middle to the long point. IMHO
    The pessimist complains about the wind; the optimist expects it to change; the realist adjusts the sails.
    William Arthur Ward

  10. #10
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    So Like this, so its basically straight, with the bottom part rounded off.

    Click image for larger version. 

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    Got it. Will practice on my 'sharpening practice' skews!
    Programmer - An organism that turns coffee into software.
    If all your friends are exactly like you, What an un-interesting life it must be.
    "A door is what a dog is perpetually on the wrong side of" Ogden Nash


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