spyderco tuff, what is the groove on the blade for?

Maniacal Pete said:
Thanks for explaining all of that Sal,
I had the same question but didn't want to ask and
appear ignorant. :o

I'm still trying to figure out how I'm going to justify the outlay,
it is a pretty pricy piece.
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Hi Pete,

We're all ignorant. that's why we ask questions. We are also students and teachers here.

You don't have to justify the cost. You just may have to wait for one. Nothing wrong with that. They'll be around for a while.
We make some very special pieces, by any standards. Not all appreciate what they are, many can't afford them, We make them just because we can. Few can afford to experience every model we create.

sal
 
Maniacal Pete said:
He did say "hardened curve."

Makes me wonder if the heat treat changes the strength along the fuller compared to a thicker piece of metal.
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Astute. When we break materials for limits, we find that steel and ceramic tend to have a "hinge". It's an area near the surface that just seems to be stronger/better at resisting the force in the break. There is argument, though theory only, that if one removes steel, such as a row of fullers, the heat treated piece might be stronger than the "full thickness" material, due to the "curves for ridigity and the "Hinge" around the curve.

I could be way off my rocker. :o Maybe we can get Cliff or Ed to share some of their thoughtsl?

sal
 
Cougar Allen said:
I don't post much in the knife forums any more because I've already said most of what I have to say....

http://www.bladeforums.com/forums/showthread.php?p=1027684&highlight=fuller#post1027684
and
http://www.bladeforums.com/forums/showthread.php?p=1027689&highlight=fuller#post1027689
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I didn't read everything in the old threads you linked to but you have a good basic explanation of different shapes and different stress conditions.

I'm a licensed structural engineer and these are actually very basic concepts in our work. In general if you take a piece of material and you remove material from it, you reduce its strength. Depending on the shape and where you remove material you might have a large affect of a very small affect, but the calculated strength will be less.

BUT, and this can be a big BUT, it also depends on the shape of the material and what the loading condition is. Material that is in tension fails in yielding and then fracture but material in compression can fail in buckling before it reaches a point where it can fail in yielding and fracture. So there are shapes and loading conditions where you can remove material and increase the strength. I don't think this would apply to a normal knife blade though.

Also consider that sometimes pieces of material with grooves in them don't just start as an original piece with a groove added, they start with a bigger piece than they might have used otherwise and then add the groove. The resulting piece might be the same weight or less than the original design, but in some aspects it can be thicker than the original piece without a weight penalty, and thus the piece with the groove is stronger. The case of the sword with a fuller vs. the diamond-shaped blade without a fuller is an example of this. Another way to view it is that the same amount of material is used but it is repositioned in the piece for more optimum use under various strength conditions.

I didn't think about the torsion case mentioned in one of the old threads, and it makes more sense for a sword than a knife.

Another aspect of the groove in the Tuff that should be considered- look at the position of the groove with respect to the hole in the blade. The hole in the blade removes material at a location where lateral bending stresses could be high so this is the limiting factor for blade strength in that loading case. The groove is not removing any material that is important to blade strength because the hole in the blade is already the limiting factor.

Personally I think it lends a unique styling element to the design of the blade. I haven't decided if I really like it or not though.
 
stabman said:
Not wrong.
I've discussed this with mechanical engineers, and they agree.
So, who's wrong? Common sense and engineers, or you?
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Better stuff was said and put better than I put it, so I removed mine, but do you have the source explaining it, is there more?
 
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sogflash said:
my very honest opinion is that the groove makes the knife look like something mantis could have designed.
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I have to take that back since the groove will help you open the blade. I don't think mantis can design anything practical, other than their laser guided knife!
 
I really like my Tuff. I found the groove helpful to deploy the blade with two hands. I am not a big fan of the large choil, I just don't ever find a need for that. I would have rather had more edge. But I still liked the knife enough to purchase one. I still have not found the perfect knife, that is why I keep buying more, although the Military is close. I am a fan of the dimples and the 4 way clip, I already changed mine to match the Millie orientation. An all titanium version might be cool, maybe there could be some spirit runs in the future.

Lastly the machining of the Spyderco logo looks neat to me.
 
bdmicarta said:
Another aspect of the groove in the Tuff that should be considered- look at the position of the groove with respect to the hole in the blade. The hole in the blade removes material at a location where lateral bending stresses could be high so this is the limiting factor for blade strength in that loading case. The groove is not removing any material that is important to blade strength because the hole in the blade is already the limiting factor.
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Quite true.
If the blade broke, it'd be at the hole, just like with every broken Strider I've seen a picture of.

So, in the case of the Tuff, it's a moot point as to the strengthening/weakening properties of fullers.

Now, we can all argue about how it looks.:)
 
duro said:
Mr Glesser, I love your knives, but the only thing that stops me from purchasing Ed's designs are the lack of jimping. Your persian for example; I would buy it in a heart beat if it had jimping.

Please tell Ed to incorporate jimping onto the thumb ramp of the blade and I will have to buy every blade that he designs.

No, I'm not a member of TNP.
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I saw a video, where Ed Schempp was interviewed by a certain knife/gear reviewer who likes to talk a lot. The interviewer, who also happens to be a big fan of jimping, adressed the issue you're talking about and Schempp answered that he, rather than putting jimping on a knife, prefers to have a handle which is shaped in a way that there is no risk of your hand slipping forwards and getting in contact with the edge, making jimping not as necessary.

Looking at the design of Ed Schempp's handles I really don't see how you could ever slip forward on them, even without jimping. What I find more difficult to understand about most of his knives, is the point of the relatively short edge to handle ratio.
 
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stabman said:
Quite true.
If the blade broke, it'd be at the hole, just like with every broken Strider I've seen a picture of.

So, in the case of the Tuff, it's a moot point as to the strengthening/weakening properties of fullers.

Now, we can all argue about how it looks.:)
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What I took away from the discussion, by inference,
was that the fuller is intended for opening the knife,
because it has an unusually strong detent.
 
Fullers stiffen and lighten a blade, they don't make it stronger. It might be a moot point to put a fuller in a folder, but if there is any advantage I want it. I've handled large fullered blade and swords. You can control the flex points on a piece with fullers, it makes pieces lighter and faster.

I was given the design criteria to make a folder that will perform with fixed blades. I wanted to use every advantage, the fuller is one of these advantages. I have found that the fuller also gives additional grip positions and other possibilities for opening the blade. I have made fullered blades where the fuller is used for opening the blade.

The grind on the blade is to the fuller, so look at this as a flat saber grind with very strong geometry.

Sals position on design, which I agree with whole heartedly, is no more than necessary, no less than perfection.

Check out the specifications on the Crucible web site and check the Charpy results on several steels. Cpm 3V was chosen like the fuller to give the best performance that can be made.

I think fullers have been covered by the posts in this thread. I think that people should handle the knife and use it to get the total picture. I seriously doubt the the limits of this knife will be tested by many of those that use the piece. It is the strongest lightest folder that with my current knowledge that I could design. Spyderco doesn't ask me for my marketing opinion or to try and make something with less performance because it is cheaper. They want the best I can do and will figure out manufacturing problems as the need arrises. They have never asked me to cut a corner or ignore a margin of better performance.

There are a lot of knives on the market that hype strength, Spyderco doesn't market this way, their basic line is stronger than most knives in production. They just do the best they can.

This knife is the best I can do to bring strength, durability, and performance to the ELU, and it is called the Tuff. It is not my nature to make insincere claims of performance. I like to think that it is not necessary, just let the piece speak for itself....Take Care...Ed
 
I am loving my tuff. Makes my sebenzas feel like toys. Don't get me wrong I still love them.
The only drawback to it is my wife is going to know this is a new knife ��
 
I don't know if anyone can answer this here but I'll ask, I have a Boye Prophet folder with a Dendritic Carbide Crystal, (Powder Metallurgy) blade, it has a relief cut into one side to assit in one hand openin', kinda shaped like a partial fuller.

My question is: How does the fuller/relief cut affect the Powder Metallurgy blade compared to regular rolled steel? Does the powdered steel, because of the way it's made, react differently to the stress forces applied in the same planes as the rolled steel?
 
The Tuff's fuller seems like it would offer excellent grip when choking up on the blade for fine work.

The strength issue doesn't cause me any practical concern, but the theory fascinates me. Since heat treatment varies with distance from the outer surfaces, this opens a door to the possibility for the fuller to actually add strength beyond an otherwise intact blade without the fuller. I know it seems unlikely and counterintuitive but new concepts always do.

The key element is the ratio between the strength at the surface and the strength of the material in the core. Consider the prosaic I-beam made from mild steel. It seems foolish to suggest that a beam of solid rectangular cross section large enough to encase said I-beam would be less strong. It would be heavier but also stronger, albeit wasteful of material.

Now consider another pair of beams whose cross sections fit into the same rectangle. One is an I-beam and the other is the full rectangle. Only these beams are not made from mild steel. No, they are made fresh each morning from flour and water with yeast. French bread with a hard, tough crust and a soft weak interior. In that admittedly extreme material the I-beam could well outperform the rectangular loaf because of it being mostly crust taking the imposed loads.

Engineers love mild steel for many valid reasons, not the least of which is the ease with which it can be subjected to calculations for determining strength. It is too easy for persons steeped in conventional engineering tradition to assume that other materials exhibit isotropy similar to mild steel. Unfortunately, the real world is more interesting and complicated than that.

All that said, I suspect that the fuller on the Tuff does not make it stronger than it would be with that material left in the blade, but the possibility is there in materials with strength differentials between surface and core.
 
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