Edges: How thin are you comfortable with?

Jason B. said:
I guess I could have stated that part a little better, edge angle does play a big part but in the current market I see blade geometry as the bigger issue, because in the long run it's a more important factor in cutting. My edge angle is about 18 DPS on folders and about 14-15 DPS on Kitchen knives. It has been a while sense I have had a Laser protractor but my actual apex angles were a few degrees high than what I was expecting from my spin heights and perceived edge angle. Edges I thought were sharpened to 10 DPS were a lot closer to 15, so unless everyone is using a laser protractor from CATRA all these numbers are inflated guesses, IMO :)
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:thumbup:

What's a bit of a measuring complication for me is with scythes, grass hooks, and hay knives the edge bevels themselves are hollow. :D But a straight line angle measurement from the edge to the shoulder is only 7-9° per side.
 
For me it's more about behind the edge thickness than it is actual edge geometry, I like them thin generally in the .005" to .010" range, but for the harder use stuff they can be in the .020" range or so.

For folders I stick with 15 to 18 DPS generally and my fixed blades that I use are in the 10 - 15 DPS depending on the actual knife.

Harder use stuff is generally 20 DPS.
 
Jason B. said:
Edge angle only plays a small part, behind the edge thickness as measured at the shoulders of the bevel is the number I concern myself with.

I like knives with a thickness of .005-.015, any thicker and you end up with a knife that wedges more and is just troublesome to sharpen. Knives today with their "tacticool" flair and edges that average .030 behind the sharpened edge using the most advance steels only makes my head hurt. It makes me think these knife makers have never performed a cutting test or have even the slightest clue as to what good cutting geometry is. Using the best steel available, grinding it like a prybar then calling it a high performance tool really burns my a$$.
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I agree with this. My thinner blades with 20dps edges cut better than my thicker blades at 15 dps. Anything with a 15-20dps edge seems to cut just fine for me, beyond that edge geometry seems to play a more important role. I suppose it depends on the medium though. Things like cardboard and watermelon tend to bind if the edge is too thick. Saber grinds and some thick blades with hollow grinds perform worse, while even my relatively thick FFG voyager XL seems to cut easily without binding.
 
One difference worth noting here is that the primary bevel is something that is only likely to see maintenance occasionally (and for most users out there, not at all) while the edge will be maintained much more frequently.
 
I actually have no idea what edge angle I've been sharpening with. I sharpen freehand, and as such haven't ever measured the angle. I have changed the secondary bevel on a number of knives that weren't cutting the way that I wanted, but again, I have no idea what it was before, or is afterwards.

How does one measure the edge angle without one of these guided sharpeners?

Oh, and I agree on the edge thickness conversation, as well as the geometry bit :).

Love me my Opinel :D.
 
I like them thin behind the edge and tend feel the sweet spot for me is between 14-17 degrees.17 seems to be my favorite for folders and most common for the knives I EDC.Thinness behind the edge makes a blade a very efficient slicer.
 
ocnLogan said:
I actually have no idea what edge angle I've been sharpening with. I sharpen freehand, and as such haven't ever measured the angle. I have changed the secondary bevel on a number of knives that weren't cutting the way that I wanted, but again, I have no idea what it was before, or is afterwards.

How does one measure the edge angle without one of these guided sharpeners?

Oh, and I agree on the edge thickness conversation, as well as the geometry bit :).

Love me my Opinel :D.
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I also sharpen free hand with stone held by other hand. I measure it by the distance between spine & stone divided with blade width (spine to edge), which gives me the tan of the angle. Based on this, my Cara Cara is about 25 inclusive. Seeing some micro chipping, I recently added aproximately 30 inclusive micro bevel. My Resilience at 30-35 inclusive has no chipping at all.
This is why I agreed with Lagrangian on how to measure convex apex angle (a long debate on another thread ;))


@ Jason & 42Blades, is it true the high carbide (Vanadium) steels cannot hold very thin edge due to carbide tearing out? If that's the case, wouldn't the benefit of high hardness & wear resistance is not helping cutting efficiency because the edge needs to be 'obtuse' or thick enough to hold the carbides?
 
An easy way to estimate your angle is by progressing in visual halves from 90°, so halve that to 45°, then to 22.5°, then to 11.25°, etc. and see where the angle you like to hold falls in that range. What I usually do, though, is I take a digital protractor ruler and slide my blade into the arms of it until the light gap between the edge of the blade and the junction of the ruler arms disappears completely and I don't feel any wiggle if I try to gently rotate the blade up and down.

Ultra-precise measuring isn't strictly necessary in most cases as much as giving oneself a decent idea of the range that the angle falls within.
 
Chris "Anagarika";14999909 said:
I also sharpen free hand with stone held by other hand. I measure it by the distance between spine & stone divided with blade width (spine to edge), which gives me the tan of the angle. Based on this, my Cara Cara is about 25 inclusive. Seeing some micro chipping, I recently added aproximately 30 inclusive micro bevel. My Resilience at 30-35 inclusive has no chipping at all.
This is why I agreed with Lagrangian on how to measure convex apex angle (a long debate on another thread ;))


@ Jason & 42Blades, is it true the high carbide (Vanadium) steels cannot hold very thin edge due to carbide tearing out? If that's the case, wouldn't the benefit of high hardness & wear resistance is not helping cutting efficiency because the edge needs to be 'obtuse' or thick enough to hold the carbides?
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I think carbide tear out happens from inferior abrasive grinding, aluminum oxide and silicon carbide are hard enough to cut the steel but not hard enough to cut the carbide, so, depending on the size of the abrasive used it will either tear the carbide from the matrix or polish it. A good indication that the stone is not cutting the steel and carbides is an excessive level of polish from the stone being used.

Unless the steel has an optimal heat treatment, which your not going to find very often, it starts at 4% vanadium but doesn't really kick most stones to the curb until 9%.

How thin you can take an edge really depends on how hard and tough the steel is. The steel needs to be very hard to support low inclusive angles and it also needs to be tough to resist impact and side loading that could cause edge failure.
 
Well, as a chef, I'm required to have some very sharp knives for cutting sashimi. I'm not even sure what angle my yanagi is set at, it's a chisel, easily my sharpest knife. I couldn't put any pressure on the edge with my bare skin.
My sujihiki is sharpened at a very wide angle, the spine is nearly touching the stone, very good slicer, cuts through proteins with ease.
On my folders, i convex them at 10 dps and slowly convex to about 15 at the edge.
I also remove a ton of shoulder off the bevel, as most my actions are slicing.
 
To further elaborate, aluminum oxide and silicon carbide are hard enough to cut all but "high-volume" vanadium carbide steels effectively. Chromium carbides are no problem. Natural stones are a more common culprit to causing unsupported carbides at the edge because they use silicon dioxide (quartz) as their primary abrasive, which is only a little harder than low alloy carbon steel run at full hardness.

Carbide tearout at low angles formed with proper stones is most likely to happen during cutting tasks with high abrasive wear, and where the size of the carbides themselves is large, which is typically an undesirable trait.
 
FortyTwoBlades said:
To further elaborate, aluminum oxide and silicon carbide are hard enough to cut all but "high-volume" vanadium carbide steels effectively. Chromium carbides are no problem. Natural stones are a more common culprit to causing unsupported carbides at the edge because they use silicon dioxide (quartz) as their primary abrasive, which is only a little harder than low alloy carbon steel run at full hardness.

Carbide tearout at low angles formed with proper stones is most likely to happen during cutting tasks with high abrasive wear, and where the size of the carbides themselves is large, which is typically an undesirable trait.
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+1

Well put.
 
The lowest I've used is 7 dps on a 2 bladed trapper. The other blade is 20 dps. I've noted no edge damage issues on it with the things I've cut with it, from wood to small diameter copper wire. The copper wire did a little damage, but it was sharpened out the next time.
 
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