What’s Wrong with this Edge?

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Look at the lines of reflection on the beautiful polished surface.  The polish is good.  The fact that the lines of reflection take a bit of a nosedive as they reach the cutting edge is a problem, and a very common one.  In this case, it is the result of aggressive work on the buffing wheel by the folks at Pfeil Swiss Made (they come pre-sharpened), but all edges eventually develop some rounding.  The wood does fight back somewhat, after all.

It’s no fun to obsess about sharpening.  The idea is to get it right and get to work.  That abrupt rounded bubble of steel behind the edge is like a water heater attached to the underside of your car; it hurts your performance.  Well, I’ve talked about the idea before in some of my other sharpening related posts.  In this one, I want to show how I go about getting an edge like this into shape.

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You can take care of it without a grinding wheel, it will just take a much longer time.  There can be a significant amount of metal to remove.  You could use a wet grinder.  I use a dry grinder.  Mine is a simple rig with an arbor and a belt that goes down to an old washing machine motor.  A friend and a hand-cranked grinder would be great.  I can never find any friends when I need to sharpen.  However you do it, just get an abrasive wheel to spin.  Disclaimer: This set up does not follow safety guidelines.  You should have a bunch of guards on yours (I live on the edge), and safety glasses, dust mask…

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I drop my Veritas grinding support out of the way for this.  It will be a freehand operation.  Notice that the left side of the wheel has a slight convex area as the edge drops off.  This can be used to create a slight hollow grind on some tools.

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Sight from above so that you can see when the bevel is flat against the wheel.  My right hand steadies the back of the handle and provides rotation.  I start in this position, then…

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rotate the gouge while maintaining contact along the bevel…

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and finish in this position.  It becomes pretty natural and you can see exactly what’s happening all along the way.  With a light touch, you shouldn’t generate much heat in the tool at all.  If you do feel it starting to heat up, cool it in water before it is hot.

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I wanted to lengthen this bevel to give the tool a lower angle of attack.  Therefore, material is being removed from the heel of the bevel first.

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Continue grinding at the same angle, keeping the bevel flat.  Of course, the last shiny area is where the tool was abruptly rounded.  Don’t be tempted to tilt the tool to grind that.  Keep grinding the whole bevel until…

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the grinding marks are even and right to the edge.

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Since I lowered the angle of the outer bevel, I add a slight inner bevel that makes sure the edge is durable enough.  I move a slip stone (here a diamond cone) across and back and forth.

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another angle

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Then sharpen on your stones like always.

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When I get to my finest stone, I work both sides of the edge lightly with a very fine ceramic slip.  This takes the most patience — I keep going back and forth from outside bevel to inside bevel until the wire edge is removed.  Sometimes you don’t see it, sometimes you do. Then I strop and get to work.

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With practice, it becomes natural.  The gouge will now sing and be much easier to touch up next time.

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6 Responses to What’s Wrong with this Edge?

  1. Grant Withington says:

    I have lost faith in pfeil somewhat.
    I recently received a pfeil v tool sharpened incorrectly to a hook at the cutting edge.
    A definite no no.
    This was a brand new tool.
    There are also issues with the resilience of the steel.
    Dissapointing

    Like

  2. Ernie says:

    Hi Dave been struggling with my new Pfeil gouge, kept sharpening it but it wouldn’t cut to please me.Finally today I went to the grinder and ground a longer bevel on it,which definitely helped.Then tonight I opened my iPad and there’s your answer to the problem. Thanks again for your advice.

    Like

  3. Tim Manney says:

    Interesting. Did we talk about this at GW fest? I sharpen them with about an 1/8″ microbevel at the edge and then lay the rest of the bevel back with a gentle roll so they scoop well and don’t get interference from the flat bevel cutting in tight curves. I mostly use them in spoon bowls, tighter curves than in your bowl carving work where that issue would be more of a problem.

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    • Dave Fisher says:

      I think that is the main difference, Tim. I am using these gouges on larger bowls without tight hollows. When I do tighter bowls, I switch to spoon-bent gouges or hook knives. I like the geometry you’ve described there for the edge. Makes sense definitely for tighter curves. Regardless, though, that abrupt rounding near the edge is bad news — and common bad news. What I like about the way you discuss sharpening is that you emphasize the underlying concepts — Why does this not work? Why does this work better than that in certain situations? How do I achieve different results? Answers to those questions are empowering beyond a set of rules and procedures.

      Like

  4. taejun jung says:

    Thank you for your useful and kindness article.
    (but, i can’t understand perfectly…. cause i’m fool in english ^^;;)

    If you don’t mind, can i ask you about your tool’s name(or brand)??
    I want to know specification(name) about “diamond cone slip stone”,”bench stone(is it DMT Dia-sharp?)”. In fact, i just entered the world of spoon and bowl carving. it is very difficult for me selecting tool…haha!

    Please give me a advise~

    Like

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