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Question about blade sharpness


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I’ve seen many videos of people’s chef knives and pairing knives melting through vegetables with no issue, seemingly like a lightsaber going through butter. 
 

Ive been experimenting with my knife sharpness and I can’t seem to achieve that laser edge. I’ve made a couple blades that are less than 1/8” at the thickest point with a distal taper down to a bit above 0. The edges are 1/32 at most before I put a real edge on em, and then I sharpen them up to 1000 grit then a strop. I would think those knives would go through vegetables like a laser but I still have to apply a bit of pressure to them through the entire cut. Nothing like that quick laser through an onion edge that I’ve seen. 
 

So I’m wondering, what really determines if the blade will have a laser like edge, I know it’s a combo of spine thickness, edge thickness, and the grit of the finished edge.

 

Anyways, my real question is how can I achieve that laser like edge sharpness? 
 

Thanks. 

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3 hours ago, Conner Michaux said:

blades that are less than 1/8” at the thickest point with a distal taper . . . edges are 1/32 at most . . .

That's still 0.125" and thicker than any kitchen knife I've made that wasn't a cleaver.  On a chef's knife, I consider a spine of 0.090" at the heel to be on the thick side, and typically go around 0.070" for the thickest part of the spine for most of my slicers.    

1/32 is ~0.0313" and this might be a bit thick as well for a finished edge on a kitchen knife.  I'll leave about that much at the edge for HT, but then when finish grinding, typically do a full face grind almost to zero before putting the final edge on so I'm about 0.015 just above the final edge.

 

 

 

Edited by billyO
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3 hours ago, Conner Michaux said:

Anyways, my real question is how can I achieve that laser like edge sharpness? 

So I guess my suggestion would be to thin down your blades a bit and see how that goes.

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I don't think a spine thickness of 1/8" is an issue. In fact if you go for full flat grinds, a spine thinner than 1/8" on a chef will run the blade too thin near the edge(for a workhorse kitchen knife like a chef). Though it's ok for specialty slicers. 

 

Your issue, like Billy said, is the edge thickness. 1/32" is too much. I thin it down to 0.005" before hand sanding. The hand sanding brings it real close to zero. 

 

if you want hair splitting sharpness, you can also sharpen a bit finer than #1000. I do hone(like you hone a straight razor, edge first and no pressure, change side every pass) my edges on finer stones for a couple of minutes as a final step just before stropping on a leather board. Stone sharpening takes some time to get right, but nothing compares ^_^

 

Edited by Joël Mercier
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Yep, what they said.

 

Sharpness is primarily about the geometry of the angle at the edge.  The smaller the angle, the sharper the blade can be.  Smaller edges are more fragile, however, so you don't want this on all blades.

 

I don't take my chef's knives quite as thin as Joel, but I do finish grind them down to about 0.010" before hand sanding.  (That is about the thickness of 3 pieces of copy paper)

 

Once you start sharpening a new blade, use your coarse stone until you have formed a wire edge, or burr along the entire edge.  (Google wire edge or burr if you don't know what to look for, there are a lot of good pics and videos out there.)  Don't stop with the coarse stone until you have that burr all the way down the edge.  Once you do, you know that you have honed the edge down as close to zero as possible with that stone.  Only then can you move to the next finest stone.  Repeat the process with progressively finer stones, and progressively lower pressure on the blade until you get to where you want to stop.

 

When you are done, it helps to pull the edge through a piece of leather or soft wood to break of any fine burr that remains.  I rarely go beyond 1000 grit on anything when sharpening. (Except my straight razor)

 

 

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Connor. This might be basic but basic is often overlooked so I thought I’d mention it. When I am still at the slack-belt grinding stage of putting an edge on, I keep looking at the edge: spine down, knife pointing away from you and towards a light source. If you can see a reflection on the edge, that is a ‘flat’ spot and needs more refining before carrying on. 

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