Upswepted Blades (persian)
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Welcome to the Wicked Forum, UpSwepted.
For a blade of the shape and character of those you’ve pictured, I would attempt to clamp them centered across the jaws, handle rotated down, in a manner that arches the blade evenly over or across the vise. I’d try to clamp the knife as high up in the jaws as I could so it’s clamped by just the jaw tips.
The tendency is for W.E. users is to try to sharpen a knife blade with one continuous sweeping stone stroke from the knife handle end to the knife tip, or from the tip to handle. With knives that are upswept like these it’s hard to do this. By always maintaining contact between the stones and the knife blade with the single continuous sweeping sharpening stroke it can’t be done without reversing the stone direction as you round the blade towards the upswept tip. I suggest you sharpen these curved blades in two or three sections. Do your sharpening strokes to smaller portions of the blade and then over lap these portions to make your sharpened edge consistent across the entire blade.
By breaking the knife into smaller sections you’ll have more control over your stone work and the direction the stones cross the knife edge. Look to keep the sharpening stroke directions so your stones move more perpendicular to the knife edge. This means the stone direction will change depending on where you’re working on the knife edge like on a clock from 10:00 to 2:00. Make your stone motion and direction match the blade shape at the section your sharpening. Don’t try to use the standard uniform single long stone sweep that you could easily use for a flat more straight edged knife, and try to make it work on these upswept blades.
Your guide rod set angle determines the bevel angle you’re applying to the knife edge. No matter from which direction the stone is moved across the knife edge as it slides up and down the guide rods. As long as you maintain flat constant and consistent contact between the stones surface and the knife edge, you can achieve this set bevel angle with the sharpening stones, as the stones slide up and down the guide rods while crisscrossing the knife edge. It’s not a haphazard crisscross sharpening stroke. Keep the stone work mostly perpendicular and evenly lined up to the portion of knife you’re sharpening at the time and your scratch patterns will be even at that portion. As your stone work follows the curve of the knife edge your scratch pattern will stay even as it follows this same curve. It’s best to try to keep your stone work even, aligned and parallel. The scratch pattern will smooth out as your go finer and finer with your grits as you blend the small sections together and it become the uniform sharp and polished edge you are striving for.
Marc
(MarcH's Rack-Its)1 user thanked author for this post.
I make a certain design of skinner that has a similar, tight radius arc to the edge and as Marc suggests, I mount them so that the arc is centered above the vise. I find that a single sweep of the stones works best. The edge is too short to make segmenting the strokes practical. Since there is no or almost no flat section to hold the stone against, you end up with point contact between the stone and the edge throughout the stroke. As such, it really doesn’t matter whether you’ve got the face of the stones perpendicular to (or parallel to) the edge. Let the stone more or less follow the edge, allowing it to rotate as it moves along the arc. When you get to the end of the stroke (tip or heel) you want to follow the line. At the heel, try to finish with the edge of the stone at the very end of the heel, or start the stroke from that end. At the tip, follow through with the stroke as you would normally – trying not to roll the face of the stone around the tip.
Here’s an example of one I’ve done. I’ve made five of these and sharpening them has been straightforward.
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