what are blood grooves for?

MIKE MACINTOSH said:
I read some ware in a story about the history of the ka-bar that the fuller was added for strength, and it helps to prevent the blade from flexing.
similer to the way the folded center section in a sheet of card board works.
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No, that's not how or what it does. The shape of the fuller does allow material to be removed while keeping strength and stiffness loss to a minimum. I can't think of a situation where removing material will add stiffness or strength.

res1cue said:
I was always under the impression that fullers are only really useful on swords, because along the length of a 25"+ blade, you could save quite a few ounces of steel! but on any average size knife, I don't see how it will noticibly lighten the blade. Did not know the bit about the aircraft survival, I had always assumed they were there because people thought they looked cool and made money
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And yet folding knife manufacturers are commonly praised for skeletonizing liners to save a few tenths of an ounce.
 
Muaddib1116 said:
No, that's not how or what it does. The shape of the fuller does allow material to be removed while keeping strength and stiffness loss to a minimum. I can't think of a situation where removing material will add stiffness or strength.
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Maybe if it were compressed inwards, creating super dense steel?
 
brandonc said:
I believe the first fuller used in a knife was as designed by Webster Marble in his ideal fixed blade, the first real hunting knife. It made the blade lighter although still stronger than most knives of the day. Kabar copied Marbles design, only with a smaller fuller that didn't really change the weight of the knife. The blood groove myth probably came about from soldiers carrying Kabars wondering what the non-functional groove along the blade was for.
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Fullers have been used on knives & swords since the Bronze age.
 
Webster Marble placed a fuller immediately behind the primary bevel in the "Ideal." (Not in the middle of the flat as on a "Ka-Bar.") He thought it reduced drag when cutting through thick meat -- as when processing game into steaks. He never mentioned stabbing, strength, or Zombies. He certainly never called it a "blood grove." However, he was not a bad marketer, and who knows what he'd say today to the innocents.
 
Cold Kill said:
Maybe if it were compressed inwards, creating super dense steel?
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I'm pretty sure this isn't possible. Liquids can't compress so I doubt a solid can unless there are voids. Can a solid be compressed enough to change the crystal structure or arrangement of molecules? I guess that is what happens with diamonds but I don't think a mechanical process is going to make that change.
 
FlaMtnBkr said:
I'm pretty sure this isn't possible. Liquids can't compress so I doubt a solid can unless there are voids. Can a solid be compressed enough to change the crystal structure or arrangement of molecules? I guess that is what happens with diamonds but I don't think a mechanical process is going to make that change.
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Yeah, pretty sure it's not actually possible on any practical level.
 
All steel is malleable to a degree(which is why wire edges can form), so if you compressed hard enough, you would eventually just kind of push the material to the side..... Although, a hard steel would probably just crack.

Muaddib1116 said:
And yet folding knife manufacturers are commonly praised for skeletonizing liners to save a few tenths of an ounce.
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I think the difference here is on a different order of magnitude. Properly skeletonized liners can reduce the weight by an ounce or two
 
FlaMtnBkr said:
I'm pretty sure this isn't possible. Liquids can't compress so I doubt a solid can unless there are voids. Can a solid be compressed enough to change the crystal structure or arrangement of molecules? I guess that is what happens with diamonds but I don't think a mechanical process is going to make that change.
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I should clarify. That was the only thing I could come it with for how a "blood groove" would be to increase structural strength. I think it may be possible (like how a super ball is compressed), but the cost of doing so for a knife would be ludicrous for the meager increase in strength.
 
Cold Kill said:
I should clarify. That was the only thing I could come it with for how a "blood groove" would be to increase structural strength. I think it may be possible (like how a super ball is compressed), but the cost of doing so for a knife would be ludicrous for the meager increase in strength.
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An easy way to model how the "blood groove" improves the structural integrity of a knife, would be to take two pieces of cardboard of equal dimensions. Cut one into an elongated U shape (kind of like a tuning fork) and leave the other piece intact. Then, twist the two pieces of cardboard. You will see that the tuning fork shaped piece of cardboard will take much more torsional force to break than the intact piece.
 
Basically by removing material from the blade, it changes how forces act along the radial axis of the knife blade. Instead of having a large amount of the force concentrated at the center of that axis, the "blood groove" is supposed to remove enough steel from that center point to allow a degree of flexibility. As a result, the torsional forces acting on the knife are concentrated on the two, thicker, pieces of steel that are located further from the center of rotation.
 
Muaddib1116 said:
And yet folding knife manufacturers are commonly praised for skeletonizing liners to save a few tenths of an ounce.
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Marketing of course!

Obviously on a large blade you could reduce the weight by much, much more with fullers than on a small folder. On a folder you can certainly shave off some weight by using lighter handle materials, skeletonized liners or no liners, and you would reduce a small amount of weight by adding fullers to the blade. Overall you might reduce the weight enough to market the knife as ultralight or something, but taking away .2 oz with a fuller really isn't going to have much impact other than on how the blade looks. So yeah I think on folders for the most part it's just tacticool marketing.
 
Cynic2701 said:
An easy way to model how the "blood groove" improves the structural integrity of a knife
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How does it improve it when material is removed? For an equal final weight and blade width, the fullered blade would be better off. But for the same stock thickness, not removing metal to make fullers leaves it stronger.
 
Cold Kill said:
I should clarify. That was the only thing I could come it with for how a "blood groove" would be to increase structural strength. I think it may be possible (like how a super ball is compressed), but the cost of doing so for a knife would be ludicrous for the meager increase in strength.
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The process is called forging, but I guess the cost would be ludicrous ... :rolleyes:

120px-Forging-fullering.svg.png
 
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