edge angle?

[krislacy]

I have just a few Spyderco's and find that my persistence is my sharpest. I have them in order below. I don't know what makes my persistence so much sharper is it the angle? Does anyone know what angle it's at? Can I do the same angle with my other knives?
1. Persistence
2. Dragonfly
3. Delica 4
4. Tasman
5. Salt
6. Ladybug salt, ladybug hawkbill, UK rescue

Thanks for the help. Kris

[chuck_roxas45]

How are you gauging your sharpness? Angle does make a difference in sharpness but it might also be how you are testing sharpness.

[krislacy]

I can shave paper not just cut it with the persistence. I take a sheet of paper and move the blade on the sheet and can cut paper off without going completely through it.

[Tsujigiri]

Factory edge is 15 degrees per side for Spyderco's. Edge geometry matters, too, though. If your D4 is the saber grind and not the FFG, then the Persistence is the only FFG grind in your list, which could account for why it slices better.

[chuck_roxas45]

I can shave paper not just cut it with the persistence. I take a sheet of paper and move the blade on the sheet and can cut paper off without going completely through it.

I do find that paper shaving relies more on dexterity than degree of sharpness. However, if you can shave paper, then you have a sharp knife. I personally don't use the paper shaving test since I cannot rely on my dexterity enough to accurately gauge my edges.

Since you are posting this here, I assume that your other knives can't. If it's not a dexterity issue, I would agree that your other knives are not as sharp but as long as your other knives don't have a crazy thick bevel(over 50 degrees), I'd say you just need to spend more time sharpening them. The steel on the persistence is pretty easy to get sharp.

There might also be a bevel issue in that because of the bevel angles on the other knives, you are not hitting the edge when you sharpen the others. All in all, if you are using paper shaving as a test, I'd say the bevel angles on your spydies are not what makes the difference in passing that test.

I hope some guys more knowledgeable than I will chime in soon.

[unit]

I can shave paper not just cut it with the persistence. I take a sheet of paper and move the blade on the sheet and can cut paper off without going completely through it.

I know what you refer to when you say shave paper. I generally find cutting paper to be an easier task than shaving it. Said another way, I can cut MANY sheets of paper with an edge that has long since degraded beyond the level of sharpness needed to shave paper.

Edge Bevel angles will go a long way to the perception of "sharpness". The smaller the angle the sharper the edge will seem. However, a GREAT deal of care needs to be taken to ensure that all else is equal.

A poorly ground edge that is very acute will rarely outperform an well ground edge with a more obtuse angle.

This is a deep subject with many variables...

[dsmegst]

Since we're talking "sharpness" as in how it can fillet paper, I think we're talking about the state of your secondary bevel (edge). Every one of those knives can get incredibly sharp and easily fillet paper or whittle hair. But at the moment, your Persistence has the best edge of all of them.

I think because 8Cr13MoV is the easiest/fastest to get sharp among your listed blade steels, I'm guessing it is being maintained the best. So as far as sharpenability (I don't think this is a real word :D ) goes, I would think VG-10 and then H-1 would follow.

I don't think edge angle matters as much here since they should all be in the same ball park. And grind differences play no part since we're not slicing through anything.

BTW, are all the knives still factory sharp?

[krislacy]

This is great. Here is more info. The delica is ffg and the dfly is zdp-189. I have touched them up a bit with the sharpmaker. The persistence is not a factory edge. I cut drywall with it and I don't recomend it. I use the brown rod thenthe white then the ultra rods then leather.

[Evil D]

Edge angle makes a huge difference. I have some knives i sharpen to ~40 inclusive, and they tend to not want to shave hair very easily, yet they'll slice through paper just as easily as my other knives. A low bevel angle can make shaving easier, but that doesn't mean the edge is sharper.

[Donut]

I think what you are seeing is the particle size and grain structure of the steels and not so much the angle of the edge. Different steels appear to cut with different performance because of the chemical makeup of the steel.

While 8Cr13MoV might be better than VG-10 for slicing paper, I am sure we can find another cutting task where VG-10 will be a better performer.

[krislacy]

Would the blade thickness make a difference too?

[chuck_roxas45]

Would the blade thickness make a difference too?

I don't think it is as simple as that. Yes, blade thickness matters, especially behind the edge thickness. But that would now depend on the materials that you are cutting. I think that sharpness is absolute meaning the width of the very apex of the edge can be the same.

Let's say both a 5mm thick blade with primary bevel angle of 40 degrees inclusive and a 2mm thick blade with a 30 degree primary bevel and both have .5 micron thickness of their edge. I would say that both knives are at the same sharpness. Cutting performance is another matter entirely. The thinner blade with the more acute angle will definitely cut thicker materials better.

BTW, a lot of people don't have a problem with getting a 40 degree inclusive bevel, hair splitting sharp.

[vvs]

Observations on my Spyderco edge angles (inclusive):
Military CTS-XHP: 30-32* (lowest angle DMT position)
ParaMilitary 2 S30V: 40* (second from lowest)
Chokwe S30V: slightly more than 40*, reprofiled to 40*
According to the blade width, where DMT mounted on blade (1"), the angles are 32 and 40* inclusive +/-. IMHO 40* is the perfect angle for S30V balanced between fine cutting and resistance to chopping/rolling.

[unit]

For filleting a piece of paper, the blade thickness (or even the thickness behind the grind) is not going to matter much. The paper thickness is going to be quite thin relative to either of these thicknesses, and the depth of the cut is going to be even thinner than the page (if the cut is to be successful). Further the separation resistance imparted by the fillet after the (which will act on the primary bevel behind the edge) would be negligible.

As I implied before, there are probably some other variables to consider for the explanation of the observation. I would look at the edge under strong magnification to reveal some answers.

Performing cuts (like filleting a page) relies heavily on the very fine scale edge geometry and the skill of the cutter. Filleting a page with a "micro" bevel, a compound bevel, or a convex edge is often going to be a more difficult cut than doing so with a single V-beveled edge. Taken to a larger scale, this concept is born out with a preference for scandi grind for bush crafters wanting to carve detailed notches in wood (the absence of fine scale complexities near the edge allows greater ease for shaving off thinner slivers of the substrate).

Another elephant sitting in the corner could be the finish of the edge. No offense to anyone, but the brevity of sharpening method description could indicate that there might be some pretty high variability in the edge finish. Was there any safeguards employed to ensure that the finish of the edges was the same?

[krislacy]

Let me think on this and respond this evening. I feel like I am at a conference with a topic I want to know about that happens to have the best speakers in the world. Thanks everyone.

[dsmegst]

As my sharpening technique becomes more consistent, I'm finding that blade steel and grind styles don't make much of a difference in the finished edge sharpness. The differences only become clear as they wear down with use. And the real difference in sharpening is in how long certain knives take to get there.

Slicing through thick material is another story though.

[jackknifeh]

I have just a few Spyderco's and find that my persistence is my sharpest. I have them in order below. I don't know what makes my persistence so much sharper is it the angle? Does anyone know what angle it's at? Can I do the same angle with my other knives?
1. Persistence
2. Dragonfly
3. Delica 4
4. Tasman
5. Salt
6. Ladybug salt, ladybug hawkbill, UK rescue

Thanks for the help. Kris

My son has a Persistance along with a few more expensive Spydercos. He gets them all very sharp but has mentioned several times that the Persistance gets sharp. All of his knives are sharp but he mentions the Persistance most often. That may be because the steel is a little softer and get sharp faster when the others require more time that he doesn't put into them. I don't know. I gave him som DMT small bench stones so he has good sharpening tools. He does have the Persistance at a very low angle he says though. Like the other guys have said there is a lot that goes into getting a sharp edge and also what makes an edge seem sharper than another. It isn't rocket science but it can get a little involved. I think it's fun though. Some cutting tasks require a very thin blade for easy slicing and some require a thicker one for strength. All need to be "sharp" but one may seem sharper or duller when cutting the same material even though both will pop hairs off your arm. Edge angle, thin behind the edge, blade thickness, grind, etc. All these things play a part in how a knife performs. That may not help much.

Jack

[unit]

As my sharpening technique becomes more consistent, I'm finding that blade steel and grind styles don't make much of a difference in the finished edge sharpness. The differences only become clear as they wear down with use. And the real difference in sharpening is in how long certain knives take to get there.

Slicing through thick material is another story though.

I agree on all points. However I might add that material consistency makes a difference also (hard vs soft vs heterogeneous).

I often laugh to myself at how complex the second simplest tool in the world really is.

I like to think that the first tool ever discovered (aside from the hand) was probably a rock used for hammering. When that rock chipped/broke, the second tool was discovered. Since that time we have consistently made improvements to the sharpened edge and our understanding of it :D

[jackknifeh]

I agree on all points. However I might add that material consistency makes a difference also (hard vs soft vs heterogeneous).

I often laugh to myself at how complex the second simplest tool in the world really is.

I like to think that the first tool ever discovered (aside from the hand) was probably a rock used for hammering. When that rock chipped/broke, the second tool was discovered. Since that time we have consistently made improvements to the sharpened edge and our understanding of it :D

The next day someone invented VG-10. His buddy discovered fire. Their wives came up with heat treating the blade in the stove. And here we are today. :) :) I should have been a history professor.

Jack

[krislacy]

Thanks everyone for such great comments. I put the leather to my already very sharp dfly zdp-189 and is real sharp now. It shaves the paper different than the persistence but I think the weight difference and blade size and how the knives are held in the hand can explain most of it. I also paid attention to how it cut through and I can now see how different steal could work better on certain material.

I worked on my ffg delica 4 but ran out of time since so much time was spent on the dfly. All knives can easily shave hair but that is not too hard for Spyderco.