ZT's, why the wide blade?

Josh K said:
Are you talking about the primary edge angle?
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No, I am talking about the secondary bevel, i.e. the cutting edge. The primary grind is the wide one that goes from the flat part near the spine down to the secondary bevel.

Hardly any knives are "zero bevel." Notable examples are the custom Emersons, where the primary grind is the cutting edge. Most knives have a secondary bevel that takes the super-acute angle that would be formed by the primary grind and brings it down to something that will last longer and be easier to maintain/repair. In the case of a really thick blade with a short primary grind, the secondary bevel must be pretty wide to get any sort of useful cutting edge. That's why the wider blades of the ZT (and others) lend themselves to better edge geometry per thickness: they utilize more distance to go from thick to thin, resulting in narrower angles and the possibility of a shorter secondary bevel.
 
puukkoman said:
No, I am talking about the secondary bevel, i.e. the cutting edge. The primary grind is the wide one that goes from the flat part near the spine down to the secondary bevel.

Hardly any knives are "zero bevel." Notable examples are the custom Emersons, where the primary grind is the cutting edge. Most knives have a secondary bevel that takes the super-acute angle that would be formed by the primary grind and brings it down to something that will last longer and be easier to maintain/repair. In the case of a really thick blade with a short primary grind, the secondary bevel must be pretty wide to get any sort of useful cutting edge. That's why the wider blades of the ZT (and others) lend themselves to better edge geometry per thickness: they utilize more distance to go from thick to thin, resulting in narrower angles and the possibility of a shorter secondary bevel.
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The possibility of a shorter secondary bevel, not the presence of a shorter (or more acute) secondary bevel. That really depends on the thickness of the blade itself, not the width of the blade.

I assumed you were talking about the primary bevel because yes, with a wider blade that tapers from a certain width to zero (assume a scandi grind for a minute) will have a more acute angle then a thinner (not as wide) blade.

Emersons aren't zero bevel, they are chisel ground. There are two bevels on the blade.
 
Josh K said:
The possibility of a shorter secondary bevel, not the presence of a shorter (or more acute) secondary bevel. That really depends on the thickness of the blade itself, not the width of the blade.

I assumed you were talking about the primary bevel because yes, with a wider blade that tapers from a certain width to zero (assume a scandi grind for a minute) will have a more acute angle then a thinner (not as wide) blade.

Emersons aren't zero bevel, they are chisel ground. There are two bevels on the blade.
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Custom Emersons are indeed "zero bevel," which is why I used them as an example. Look it up. I am aware that the production versions are chisel-ground, and that is irrelevant.

Yes, possibility of a shorter secondary bevel. That's what I've been saying. To illustrate this, I used the example of a knife with zero secondary bevel, which is (of course) the smallest secondary bevel possible... zero.
And, the whole point is this:
You have two pieces of steel, one being 1/8" thick and 1" wide, and the other being 1/8" thick and 1.5" wide. If you grind them to a sharp edge, while still maintaining the maximum width of each, and starting at the spine (or at least at the same distance from it), the wider piece will have a more acute angle at the edge.
Period.
It's simple geometry.

When you apply a secondary bevel to an edge, you make it more obtuse so that it lasts longer and is easier to maintain. Now say you want to apply the same secondary bevel to the two pieces. If the initial angle of the first piece is more obtuse, then its secondary bevel will appear to be longer than that of the second piece. This is because, at any given distance from the sharp edge, the 1"-wide piece of steel will be comparatively thicker than the 1.5"-wide piece at the same distance. That increase in thickness vs. distance is essentially what makes a "good slicer."
 
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puukkoman said:
Custom Emersons are indeed "zero bevel," which is why I used them as an example. Look it up. I am aware that the production versions are chisel-ground, and that is irrelevant.

Yes, possibility of a shorter secondary bevel. That's what I've been saying. To illustrate this, I used the example of a knife with zero secondary bevel, which is (of course) the smallest secondary bevel possible... zero.
And, the whole point is this:
You have two pieces of steel, one being 1/8" thick and 1" wide, and the other being 1/8" thick and 1.5" wide. If you grind them to a sharp edge, while still maintaining the maximum width of each, and starting at the spine (or at least at the same distance from it), the wider piece will have a more acute angle at the edge.
Period.
It's simple geometry.
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EmersonErnest_CQC6_2000.jpg


I see a secondary bevel, not sure what you see.

Yes, it will have a more acute angle with everything being the same at a full zero (scandi) grind. I'm not sure what you're debating there.

The thickness of the blade has more to do with the height of a secondary bevel for a given angle (30*, 40*, whatever) then the width of the blade unless you're putting a full zero grind on the blade.
 
Looks like a shadow to me.
5033-9490.jpg

There you go. No secondary bevel.
But really that's not the point. The angle is the point.

You don't have to draw anything, I think we're both saying the same thing. It's hard to have a good discourse over the internet with expressionless words instead of voices.
 
I love the way half of the people in here are talking about how thick the blade is, half are talking about how broad the blade is; but it doesn't seem to matter because nobody is listening to each other.
 
I think both sides are talking about the same thing: you can have a blade with a thick spine but a thin (acute) edge when the blade is wide.
 
FlaMtnBkr said:
Ok now the why.

Why is this axis neutral?
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Here is the genesis of the term "neutral axis."

Imagine a simple beam of rectangular cross section resting on two supports, one on each end. A load is applied in the center of this beam, heavy enough to deflect it a bit, but not enough to break it. Let us imagine that this beam is made of steel.

Because it is deflected downward in the center, the top of the beam is under compressive strain and is actually shorter than before the load was applied. The bottom of the beam is under tensile strain and is actually longer than it was before the load was applied.

As you move from the top of the beam towards the bottom, the degree of compression reduces. As you move up from the bottom edge of the beam the tensile forces reduce. In the middle of the beam's height there is no tensile or compressive force. This middle portion of the beam is called the neutral axis. Neither positive nor negative, compression nor tension, the longitudinal strain in the middle is neutral.

Bill
 
FlaMtnBkr said:
What is a neutral axis? Does my knife have one?

Seriously, what is a knife's neutral axis???
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In structural terms, the neutral axis of a member in flexural stress is the section where there is no stress or strain.

Consider the example of a rectangular wood beam (rectangular in cross-section). Looking at the loaded beam from the side, its deformed shape is that of a 'smile'. It bends into a curve. In order to achieve that shape, the fibers toward the top of the beam have to compress and the fibers toward the bottom have to lengthen. The fibers at the center do neither, and that is the neutral axis.

How this figures into my statement, relates to a property of structural members that's known as "section modulus". Do a Wiki search on that term if you like. Without going into too much detail, section modulus describes the geometric strength of a cross section as a function of its geometry. All other things equal, a stronger cross section will have mass located relatively distant from the neutral axis.

You know what an "I-beam" looks like? That is called a wide-flange beam. The flanges are the horizontal parts of the beam, located at the top and bottom. That cross-sectional shape is significantly stronger than a basic rectangle comprised of the same area. The reason for that is because the flanges concentrate material at relatively great distance from the neutral axis. Back to the wood beam, that material would be the fibers undergoing the greatest tension and compression forces. So concentrating material out there is putting it to the best use.
 
Thanks for the insight guys. I appreciate the points about the primary and secondairy bevels. I'd just bought a ZT 302 and was wondering about it.
 
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