drawing the burr & clamping scaluped top knife
- This topic has 5 replies, 4 voices, and was last updated 06/30/2018 at 1:52 am by
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I guess I would ask what type of edge it is and which grit stone are you using to produce the first burr? I think it might be possible that with a coarse grit and a hard steel, the edge might be breaking off before ever forming a burr. Really coarse grits can tear the edge off under the right circumstances, especially where the stone has not been completely “broken-in.” I’m assuming here that you are seeing the black marker being completely erased by the stones. Check the edge with a jeweler’s loupe or a magnifying glass to see if the marker is actually being removed at the very edge. If you’ve been stoning one side for a long time but can’t feel a burr, you ought to be able to see an obvious difference in the bevel widths.
As for your second question, can you post a photo of the knife blade?
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That knife looks like it should be relatively straight forward to clamp. The knife doesn’t have to touch both the pins, it is perfectly fine to have the knife resting on only one (or neither) of the pins.
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You may be able to clamp with the rear most spine point between the two pins while resting on both pins. Like Organic said, you really don’t need to use any of the pins. Resting on just one pin gives you a good repeatable position when you measure the knifes clamping orientation in the jaws relative to the pin. Use your alignment guide or advanced alignment guide to make some other relationship measurements to help you to recreate this mounting position for repeatability and touch ups.
Remember just because the knife clamped easily and well in a certain position doesn’t necessarily mean that’s the best sharpening position for the knife. Other issues need be considered also. Will that clamping position allow for the most efficient coverage and sharpening of the entire edge, (i.e. the sweet spot)?
Marc
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I have a small SOGWinder I folder which is very thick relative to its grind angle and has an unusually high distal taper. It also has the problem of offering very little surface on which to clamp. I remove the thumb stud and clamp on the only areas on which I can get a bite. I’ve run into a number of knives which seem to be configured specifically to annoy me, but there always seems to be a way. Here’s a photo of the knife with the thumb stud:
And if you look close enough, here’s a photo of the knife in my Gen 1 vise:
It’s important to keep the blade from moving, so I normally use a tape (foil or masking) to prevent slippage. You don’t need to make full contact with the entire face of the vise, but you’ll need to make sure the jaws make contact with the blade at their top edge .
From a physics standpoint, the area of contact between two surfaces which will slip relative to one another is not a factor. What does matter is the force applied between the two surfaces and the coefficient of friction between them. Contact area matters when the two surfaces are in traction with each other, as in a rubber tire on a porous concrete surface – the more area, the greater the amount of traction.
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