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Sharpen a very curved blade

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  • #47217
    Michael Blakley
    Participant
    • Topics: 27
    • Replies: 26

    A friend handed me a knife and asked me to sharpen it for him.  The blade is severely curved.  If the arc of the blade was turned into a circle it would be about the diameter of a basketball.  The total length of the cutting edge of the knife is about 8 inches long.  It’s made of 440 steel.

    The blade is really dull.

    If it were a straight blade, I’d be done with it already.  But I don’t want to do anything to it because it’s curved.

    What advice can you give me about sharpening a severely curved blade?

    Faithfully Yours.

    FP

    #47219
    MarcH
    Moderator
    • Topics: 59
    • Replies: 2102

    I’d attempt it by clamping it centered in the jaws to balance the amount of the arc of the blade forward and behind and below the jaw center and jaw line, in a manner that a line imagined between the knife edge right at where the heel meets the handle and the tip of the knife blade is parallel to the jaw line.

    Sounds like your describing a knife like this.https://www.amazon.com/Victorinox-Cutlery-8-Inch-Curved-Breaking/dp/B0019WXEO2/ref=sr_1_5?ie=UTF8&qid=1533914485&sr=8-5&keywords=curved+filet+knife

    If the knife ends, (i.e., heel and tip) hang too low below the jaw line when clamped so that the stones can’t meet the knife edge to work efficiently, you may need to elevate the knife higher above the jaw line still clamping it similarly but with the LAA.  Also if the radius of the arc is not quite uniform like this knife style I linked in blue above, you may need to adjust the knife clamping position by tilting the handle up or down, or possibly shifting it fore or aft in the jaws, (i.e., moving the imagined line between tip and heel off of parallel to jaw line), in order to position the knife it a “sweet spot”.  You can verify this position and stone efficiency with a sharpie on the bevel.

    Marc
    (MarcH's Rack-It)

    #47220
    Organic
    Participant
    • Topics: 17
    • Replies: 929

    Regardless of blade shape, the process for finding the sweet spot is the same as is outlined in the WE manual and in Marc’s thread. I recall that Alan sharpened a mezzaluna knife not too long ago, so I know that really curved blades can be sharpened on the WE.

    An even more extreme case of curved blade:

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    #47221
    Michael Blakley
    Participant
    • Topics: 27
    • Replies: 26

    Here’s a photo of the knife.

    Michael

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    #47223
    tcmeyer
    Participant
    • Topics: 37
    • Replies: 1928

    That’s a really pretty knife.  I’ve done this curved parer for my sister a couple of times and have had no problems getting it sharp, using standard WE diamond stones – and not the round ceramic 600.  It’s a lot tighter radius than the above knife.  One caveat is to use both corners of the stone as you sweep along the edge.  If you roll the stone and work with a single corner, the angle will  change slightly.  Since the radius around the slide rod at the corners is greater than at the face, the angle will decrease.  How much different is dependent on the radius of the curved edge, but in any case, it’s a small number.

    hook knife view 1 comp'd

     

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    #47224
    MarcH
    Moderator
    • Topics: 59
    • Replies: 2102

    Michael which WEPS model do you use?  Is the top side forward of the spine and behind the tip beveled and sharpened, also?  If it is I’d do that part first.  Exercise care at the tip to keep from rounding it.  When finished with the top bevel, I’d tape it for protection because you’ll be clamping close to that blade portion when you flip it and clamp it to sharpen the main bevel, curve up.   It looks pretty dang symmetrical.  Shouldn’t be too tough to clamp it centered. I’d attempt it how I suggested above.  It can be sharpened with patient, care and due diligence.  It says 440 stainless which is pretty hard, (HRc 60), and should sharpen fairly well and not too difficultly.

    Marc
    (MarcH's Rack-It)

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