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TOPIC: Suggested/Factory Angle not Jiving w/Sharpie?

Suggested/Factory Angle not Jiving w/Sharpie? 3 months 1 week ago #15342

  • tcmeyer
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Maybe this will help to understand what you're seeing...or maybe it won't.

The bevel angle is fixed only on a circular line projected radially around the center of the pivot point and offset by half the thickness of the block. Anytime you leave that arc of travel, the angle changes.

As the block follows the curve of a blade, the actual bevel angle rotates with the block, which tends to remain flat against the blade and aligned with, but offset to the pivot point.

To see this clearly, take a block with your hand and hold it against the top edge of the vise. Look at the angle and see what the bevel would be. Now take the block and rotate it away from you and hold it against the opposite (vertical) side of the vise. Now look down on the block and see what the bevel angle would be. Not the same, is it? This is the geometry effect that changes bevel angles as the blocks move along a blade.

I first saw this when I tried sharpening a very long jerky knife, which is completely straight and about 12" long. It was obvious that the bevel angle at the far tip was going to be higher than nominal. I also noted that if the tip had curved down, the bevel angle would have been lower than nominal.

When you select an angle for sharpening any knife on the WE rig, you have to accept that this is a nominal, and that actual bevel angles produced along the edge are variable, depending on the curve and length of the blade and its position in the vise. The big advantage of the WEP is that the angles are smooth, flat and repeatable.

By the way, jerky knives are known to remove bits of fingertips at the far extension of the rods. Always keep your fingers behind the block face - don't leave your pinkies dangling.
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Suggested/Factory Angle not Jiving w/Sharpie? 3 months 1 week ago #15343

  • JDS
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Thank you so much for the info, I think I get it but going to spend some time processing the principals you shared. Sorry if i'm beating a dead horse.

May I just ask one question... if you put my Hinderer XM-18 w/a known factory angle of 22 degrees, what degree range would you expect YOUR arms to be at to start in YOUR WE to remove marker properly from the edge?

Thank you for your time.
Last Edit: 3 months 1 week ago by JDS.
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Suggested/Factory Angle not Jiving w/Sharpie? 3 months 1 week ago #15345

  • tcmeyer
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The fact is that you don't have a "known factory angle of 22 degrees." You have a "recommended factory angle of 22 degrees."

The Sharpie marker is not used to find a correct angle. It is used to tell you when you have reached the existing apex of the knife edge. You continue to stone the edge just until the marker is removed at the very edge. Removing less means that you are not yet sharpening the edge. Removing more means that you are removing unnecessary metal and may be moving the apex beyond the centerline.

You can read much more specific details on WEP geomtry and the effects on dihedral angles by reading AnthonyYan's post, just updated. But you have to be smarter than me. I have ADD and have to figure things out for myself.

If I had your Hinderer XM-18 in my WEP rig, I'd clamp the blade, spine held down on the two pins roughly centered over the vise, record the distance from the vise to the tip, set the angles at 22 degrees, sharpen it to a fine, polished edge and expect the owner to be very pleased.
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Suggested/Factory Angle not Jiving w/Sharpie? 3 months 1 week ago #15347

  • LeoBarr
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You are quite right many knives have recommended factory recommended bevels it is a guide nothing more since most manufactures do not sharpen with a set bevel it is done freehand on wheels or belts ; Kai shun is a classic example the recommended bevel is 16Ëš( - considering most people do not have a controlled angle way of sharpening this is a guide to aim for although 16Ëš over 15Ëš is negligible that is a sales ploy ).
Shuns are sharpened by hand on a machine so they are approximately 16Ëš +/-2Ëš.
So the sharpie trick is highly unlikely to yield the same angle as the recommended one especially on both sides.
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