Sal, why is the Delica ground so thick behind the edge ?

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guywithopinion
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Re: Sal, why is the Delica grinded so thick behind the edge ?

#21

Post by guywithopinion »

jpm2 wrote:
Mon May 28, 2018 8:02 am
How do you make the primary FFG any thinner given a set thickness and height? I must not understand geometry too well.
I'm not an edge nut exactly. However, the basic geometry could go something like this. Say you start out with 2.5mm by I dunno, 25mm blade stock. A full flat grind simply means the primary grind goes the whole way down the blade stock at a consistent angle. If you made two knives, you could grind one where it is 2.5mm on the spine side, and is only 0.5mm on the edge side. You could grind the other where it is 2.5mm on the spine side and is 1.5mm on the edge side. Then you take both and put a 17 degree per side secondary bevel (the actual edge) on both. Both knives are the same size, both FFG from 2.5mm stock, both have a 17-degree edge on them. But one will be much thicker behind the edge. And the secondary bevel on one will look much wider than the other, in spite of being at the same angle.

I'd also point out that you could have say 2.5mm by 50mm stock (i.e. the blade will be wider from edge to spine). Perhaps you grind that at the same angle as the previous example that ends up being 1.5mm. Now it will only be 0.5mm at the edge, exactly the same thickness at the edge as the previous more acute knife. Except they have very different blade design. (I am not qualified to say which will cut better, etc).
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Re: Sal, why is the Delica grinded so thick behind the edge ?

#22

Post by MichaelScott »

It would appear that the angle of the flat grind and subsequent thickness at the edge depends directly on the height of the piece ground given the widths are the same.
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Re: Sal, why is the Delica grinded so thick behind the edge ?

#23

Post by Evil D »

MichaelScott wrote:
Mon May 28, 2018 6:15 pm
It would appear that the angle of the flat grind and subsequent thickness at the edge depends directly on the height of the piece ground given the widths are the same.

Precisely.

Image


But, given the same blade thicknesses between the two, both will get even thinner if the blade stock is made thinner.
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Re: Sal, why is the Delica grinded so thick behind the edge ?

#24

Post by Pelagic »

JEEZ SAL. WHY DO YOU HAVE TO MAKE FOLDING PRYBARS LIKE THE DELICA?

Lol. You can't win em all.
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Re: Sal, why is the Delica grinded so thick behind the edge ?

#25

Post by jpm2 »

guywithopinion wrote:
Mon May 28, 2018 6:04 pm
jpm2 wrote:
Mon May 28, 2018 8:02 am
How do you make the primary FFG any thinner given a set thickness and height? I must not understand geometry too well.
I'm not an edge nut exactly. However, the basic geometry could go something like this. Say you start out with 2.5mm by I dunno, 25mm blade stock. A full flat grind simply means the primary grind goes the whole way down the blade stock at a consistent angle. If you made two knives, you could grind one where it is 2.5mm on the spine side, and is only 0.5mm on the edge side. You could grind the other where it is 2.5mm on the spine side and is 1.5mm on the edge side. Then you take both and put a 17 degree per side secondary bevel (the actual edge) on both. Both knives are the same size, both FFG from 2.5mm stock, both have a 17-degree edge on them. But one will be much thicker behind the edge. And the secondary bevel on one will look much wider than the other, in spite of being at the same angle.

I'd also point out that you could have say 2.5mm by 50mm stock (i.e. the blade will be wider from edge to spine). Perhaps you grind that at the same angle as the previous example that ends up being 1.5mm. Now it will only be 0.5mm at the edge, exactly the same thickness at the edge as the previous more acute knife. Except they have very different blade design. (I am not qualified to say which will cut better, etc).
Thanks, I understand now.
Let's say the delica was taken to a zero edge from the spine (no reduction in spine width). I wonder how much reduction in width there would be measuring 1/4" from the cutting edge.

What if 10 minutes was spent on a coarse stone thinning the shoulders?
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Re: Sal, why is the Delica grinded so thick behind the edge ?

#26

Post by zhyla »

Evil D wrote:
Mon May 28, 2018 6:26 pm
MichaelScott wrote:
Mon May 28, 2018 6:15 pm
It would appear that the angle of the flat grind and subsequent thickness at the edge depends directly on the height of the piece ground given the widths are the same.

Precisely.

Image

But, given the same blade thicknesses between the two, both will get even thinner if the blade stock is made thinner.
Well... there’s more to thickness behind the edge than that diagram shows. Prior to adding the secondary bevels there is a flat at the bottom rather than a point. How wide that point is affects the thickness behind the edge once you add secondary bevels to get the edge.

This is why identical stock and blade height can yield different thickness behind the edge measurements.
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Re: Sal, why is the Delica grinded so thick behind the edge ?

#27

Post by guywithopinion »

MichaelScott wrote:
Mon May 28, 2018 6:15 pm
It would appear that the angle of the flat grind and subsequent thickness at the edge depends directly on the height of the piece ground given the widths are the same.
Only if it were a zero grind. Two pieces of identical height and width could be ground to different thicknesses behind the edge in an FFG.
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Re: Sal, why is the Delica grinded so thick behind the edge ?

#28

Post by Bill1170 »

We’ve already established that the Delica is a knife for a broad market. Spyderco has to balance performance (thin BTE) and durability (less thin BTE). In the FFG Delica they sell a knife that is more performant than most comparable OHO modern folders.

We knife knuts are a tiny percentage of the market Spyderco serves. If a Delica seems too conservative in its edge geometry, we have a few good choices, including:
1) Choose a different knife.
2) Modify the knife to your preference.
3) Hire another to modify your knife.

My first Delica was a saber ground ZDP D4. Great knife, but not a great cutter. I opted for #2 above and hand-convexed it to a zero edge with a mirror polish, all on bench stones. Now it’s a laser. It took hours to do, but was very rewarding.
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Re: Sal, why is the Delica grinded so thick behind the edge ?

#29

Post by Evil D »

zhyla wrote:
Mon May 28, 2018 8:34 pm
Evil D wrote:
Mon May 28, 2018 6:26 pm
MichaelScott wrote:
Mon May 28, 2018 6:15 pm
It would appear that the angle of the flat grind and subsequent thickness at the edge depends directly on the height of the piece ground given the widths are the same.

Precisely.

Image

But, given the same blade thicknesses between the two, both will get even thinner if the blade stock is made thinner.
Well... there’s more to thickness behind the edge than that diagram shows. Prior to adding the secondary bevels there is a flat at the bottom rather than a point. How wide that point is affects the thickness behind the edge once you add secondary bevels to get the edge.

This is why identical stock and blade height can yield different thickness behind the edge measurements.


Well yes of course the edge bevel contributes to how thick the blade is. I made that diagram for another argument about taller blades vs shorter blades.
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Re: Sal, why is the Delica grinded so thick behind the edge ?

#30

Post by Termite Toothpick »

Try a Chaparral, very thin blade, very nice slicer...

I know...not part of the question at hand, but I think others have said it already...Delica made for the average joe. If you want a slicer, look for that. And the awesome thing about Spyderco is you have many options out there, and that is great!
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Re: Sal, why is the Delica grinded so thick behind the edge ?

#31

Post by mb1 »

To the made for the average user/abuser points...I think as we progress deeply (down the rabbit hole) into the knife hobby, we forget how little other people know or care about knives.

When I was shopping for my first Spyderco, I happened to mention it to a coworker. Now mind you, this guy is considered smart here at work. He shoots and hunts a little. He said he had a Spyderco and it wouldn't stay sharp. He even had it sharpened by "the guy at the Farmer's Market with the sharpening booth." His advice? "Get a Case man. They stay sharp a lot longer." Of course he couldn't tell me the steel type, let alone the model he owned.
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Re: Sal, why is the Delica grinded so thick behind the edge ?

#32

Post by zhyla »

Termite Toothpick wrote:
Tue May 29, 2018 8:54 am
Try a Chaparral, very thin blade, very nice slicer...
There's one in the mail. It's going to trigger a collection reckoning though.

Evil D wrote:
Tue May 29, 2018 4:36 am
Well yes of course the edge bevel contributes to how thick the blade is. I made that diagram for another argument about taller blades vs shorter blades.
Oh, my mistake, I thought you were talking about primary bevel height, not secondary. I should make a fancy diagram one of these days...
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Re: Sal, why is the Delica grinded so thick behind the edge ?

#33

Post by Donut »

I still want to see a non-distal taper FFG Delica/Endura.

Different question, same answer: It is MUCH more difficult to add material to a knife than it is to remove material.
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Re: Sal, why is the Delica grinded so thick behind the edge ?

#34

Post by Evil D »

Donut wrote:
Tue May 29, 2018 5:14 pm
I still want to see a non-distal taper FFG Delica/Endura.

Different question, same answer: It is MUCH more difficult to add material to a knife than it is to remove material.

I wish distal taper would go away for most models, especially wharnies. If the grind is thin enough you still get a nice sharp tip, they're just a bit more robust.
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Re: Sal, why is the Delica grinded so thick behind the edge ?

#35

Post by zhyla »

Couldn't sleep this morning, drew a diagram.

Image

The diagram is obviously just to show what thicker and thinner mean. There are three measurements at play here: the stock thickness, the thickness behind the edge, and the secondary bevel angle/height. The primary angle is equivalent to the thickness behind the edge but in practice we just measure the thickness.

To the naked eye the thick/obtuse and thin/acute can look identical. It isn't until you actually measure the secondary angle that it becomes apparent why your knife performs the way it does.

If you've got a reasonably acute angle (25 - 35 included angle/12.5 - 17.5 dps) then the secondary bevel height is a good clue what's going on with the blade thickness. Tall secondaries look beautiful and we love seeing those polished and photographed, but they're basically just wasted thickness for most users. You need some visible bevel though or sharpening gets tricky.
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Re: Sal, why is the Delica grinded so thick behind the edge ?

#36

Post by gaj999 »

Evil D wrote:
Mon May 28, 2018 4:41 pm
Well case in point, it WAS a full zero grind originally but too many complaints about chipping and edge fractures led them to giving it a small bevel. It is still near a zero grind, it's just thicker behind the edge than you expected because the blade stock is so thick and the blade height is so low, it's a wedge.
No. See the geometry posts for why I have a wide secondary bevel on my Nilakka now ... Near zero doesn't give me a 0.1" bevel at 10dps. Unless by "near" you mean "not even close". Doesn't matter and I shouldn't have even posted since I'm pretty much done with Spyderco at this point unless the value proposition improves. Having to regrind an expensive knife just to get it to cut as well as a $10 Opinel or a $25 SAK just grates on me.
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Re: Sal, why is the Delica grinded so thick behind the edge ?

#37

Post by Evil D »

gaj999 wrote:
Thu May 31, 2018 12:00 pm
Evil D wrote:
Mon May 28, 2018 4:41 pm
Well case in point, it WAS a full zero grind originally but too many complaints about chipping and edge fractures led them to giving it a small bevel. It is still near a zero grind, it's just thicker behind the edge than you expected because the blade stock is so thick and the blade height is so low, it's a wedge.
No. See the geometry posts for why I have a wide secondary bevel on my Nilakka now ... Near zero doesn't give me a 0.1" bevel at 10dps. Unless by "near" you mean "not even close". Doesn't matter and I shouldn't have even posted since I'm pretty much done with Spyderco at this point unless the value proposition improves. Having to regrind an expensive knife just to get it to cut as well as a $10 Opinel or a $25 SAK just grates on me.


Are you trying to say a zero grind is 0 degrees? Because that's impossible. Your wide bevel is due to the BLADE GRIND being steep, and it's wide because it's only a few degrees off from your 10 degree bevel. Zero grind just means the blade grind comes all the way to the edge apex, which the original did.
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Re: Sal, why is the Delica grinded so thick behind the edge ?

#38

Post by Evil D »

gaj999 wrote:
Thu May 31, 2018 12:00 pm
Evil D wrote:
Mon May 28, 2018 4:41 pm
Well case in point, it WAS a full zero grind originally but too many complaints about chipping and edge fractures led them to giving it a small bevel. It is still near a zero grind, it's just thicker behind the edge than you expected because the blade stock is so thick and the blade height is so low, it's a wedge.
No. See the geometry posts for why I have a wide secondary bevel on my Nilakka now ... Near zero doesn't give me a 0.1" bevel at 10dps. Unless by "near" you mean "not even close". Doesn't matter and I shouldn't have even posted since I'm pretty much done with Spyderco at this point unless the value proposition improves. Having to regrind an expensive knife just to get it to cut as well as a $10 Opinel or a $25 SAK just grates on me.


Here ya go. I guess take it up with Spyderco, maybe they don't know what they're talking about :rolleyes:


"Made from premium CPM S30V stainless steel, the Nilakka’s blade features full-flat-ground bevels that flow smoothly into a zero-ground cutting edge."


https://www.spyderco.com/catalog/detail ... roduct=780
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Re: Sal, why is the Delica grinded so thick behind the edge ?

#39

Post by gaj999 »

Evil D wrote:
Thu May 31, 2018 12:23 pm
Here ya go. I guess take it up with Spyderco, maybe they don't know what they're talking about :rolleyes:
That's correct. They don't. False advertising pisses me off. This is pointless. I'm bowing out again. Back in another six months or so ... maybe
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Re: Sal, why is the Delica grinded so thick behind the edge ?

#40

Post by Evil D »

gaj999 wrote:
Thu May 31, 2018 12:26 pm
Evil D wrote:
Thu May 31, 2018 12:23 pm
Here ya go. I guess take it up with Spyderco, maybe they don't know what they're talking about :rolleyes:
That's correct. They don't. False advertising pisses me off. This is pointless. I'm bowing out again. Back in another six months or so ... maybe


Sounds more like a false understanding of what a zero grind really is but whatever man. Don't take life so seriously.
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