How do blood grooves improve a sheath knife?

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Captain O

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If acts as does an I-beam it would be requred on both sides of the blade to increase structural rigidity. What other advantages are gained from the blood groove?

Captain O
 
In my opinion, 'blood grooves' are hangovers from the days when fullers (which is what they are) were used to lighten swords. There are a lot of myths surrounding them, and I don't think they serve a useful purpose at all.
 
Jack Black said:
In my opinion, 'blood grooves' are hangovers from the days when fullers (which is what they are) were used to lighten swords. There are a lot of myths surrounding them, and I don't think they serve a useful purpose at all.
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+1

They might look cool or make the blade lighter. They do not add strength.
 
You can use a fuller to reduce the weight of a blade without reducing the rigidity as much as you would if you took a commensurate amount off the blade stock as a whole.
 
Jack Black said:
In my opinion, 'blood grooves' are hangovers from the days when fullers (which is what they are) were used to lighten swords. There are a lot of myths surrounding them, and I don't think they serve a useful purpose at all.
Click to expand...

Yea I think some just enjoy the cosmetic look of it, others like perpetuating those myths.
 
Dad's custom Buck General (with an added inch) by "Daddy Buck" himself, had a "blood groove". The groove didn't impress him. He used the General throughout WWII and Korea, leaning upon it heavily in the Pacific theatre. It made for a great "deck knife" too.

Captain O
 
Back in the day blood grooves were used to help prevent "stiction" on the battlefield when the blade was withdrawn. Supposedly it allowed some air in, reducing the suction created by the blood when the blade was pulled out.
 
afishhunter said:
Back in the day blood grooves were used to help prevent "stiction" on the battlefield when the blade was withdrawn. Supposedly it allowed some air in, reducing the suction created by the blood when the blade was pulled out.
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I think this is the most common myth relating to fullers on knives.
 
afishhunter said:
Back in the day blood grooves were used to help prevent "stiction" on the battlefield when the blade was withdrawn. Supposedly it allowed some air in, reducing the suction created by the blood when the blade was pulled out.
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Pretty sure our bodies rely on positive pressure in the blood vessels, so I fail to see how suction would be created. If anything, the blood would be trying to push the knife back out.

also, as someone else noted, an I beam is not stronger than a solid beam, it's nearly as strong but considerably lighter. U channels (having a fuller on only one side) are also weaker than a solid beam, and they take stresses better in one direction than the other.

But on a pocketable knife or smaller sheathed knife, there's likely no functional advantage. On a machete or knife of considerable length and girth, a case can be made for adding a fuller to lighten the blade, but in my opinion, "Blood grooves" are a mall ninja fabrication and a blade with fullers will always be weaker than a blade without them.
 
Captain O said:
If acts as does an I-beam it would be requred on both sides of the blade to increase structural rigidity. What other advantages are gained from the blood groove?

Captain O
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You cannot ever INCREASE strength or rigidity by removing material from a structure. It will always weaken the structure and cause it to bend easier.

You can design a structure that has less material in low stress areas and more material in high stress areas to have a stronger/more rigid structure PER UNIT OF MASS. This is the concept begging I-beams: to be strong/resist bending in one direction while still remaining relatively light.

The thing about I-beams is that they are designed to be strong in one axis only. The upper and lower flanges on an I-beam are loaded in compression (the flange on the inside of the bend) and tension (the flange on the outside of the bend) and the web is put into torsion (internal shear) between the flanges trying to resist the growing/shrinking of the flanges as they are loaded.

If a blade with a fuller makes a rudimentary I-beam then the blade would theoretically be stronger (per pound) with forces parallel to the blades (cutting/chopping) but weaker in side-loading.

Since most knives that break mid-blade are due to excessive side loading, I would say a fuller is a bad design if you are attempting to increase strength in a knife.

In a sword you get a lot higher edge loading and weight saving is more critical so I could see an argument where a fuller would be desirable.
 
Article by Joe Talmadge on A.G. Russell's Website



Author: Joe Talmadge

What is a Blood Groove For?
This question comes up every 8 months or so. The blood groove on a knife probably is derived from the channel present on swords, where it is called a "fuller". There are some persistent myths floating around about the function of blood grooves, from "releases the vacuum when the knife is thrust into a person" to "no functional use, purely decorative". Let's talk about these wrong answers first, before we talk about the right answers.

Wrong Answer #1: Releasing the Body Suction

Basically, this theory postulates that the blood groove is present to facilitate withdrawing the knife from a person/animal. In this scenario, it is said that the animal's muscles contract around the knife blade, and that this causes a vacuum, which makes the knife difficult to withdraw. But on a knife with a blood groove, blood runs through the blood groove and breaks the suction, so the knife can be withdrawn with less difficulty.

One problem is that there's no evidence that this suction ever really happens. Also, over and over again people report that there is no difference whatsoever in the difficulty of withdrawing a knife with a blood groove vs. one without. This is one theory that has been tested and found wanting.

Yes, I realize you may have heard this myth from your deadly knife instructor, or read it in a book somewhere. But the experts agree that it is false. If your knife can cut its way in, it can just as easily cut its way out, with or without a blood groove.

And with that, I am going to change terminology from "blood groove" to "fuller", since we all now know the so-called "blood groove" is not playing a blood-channeling function.

Wrong Answer #2: Purely Decorative

There is a grain of truth to this one. Although a fuller does play a functional role, on a short knife the effect might be so small as to be insignificant. Many believe the fuller plays a strictly decorative role on knives or swords under 2 feet long. As the knife or sword gets bigger, the fuller plays an increasingly important role. On smaller knives, it is indeed probably just decorative.

Right Answers:

Okay, so what substantive role does the blood groove/fuller play? The bottom line is, it does two things:

1. It stiffens the blade 2. It lightens the blade

That first statement has been the subject of some controversy, with some people sending me equations purporting to show that the removal of material cannot make the blade stiffer. I will table for now the question of "does the blade get stiffer, in some absolute sense, due to the fuller?" Rather, I'll weaken the claim to say that the blade *feels* stiffer to the user who is waving it around -- because it's stiffer for its weight.

I'll reproduce a post by Jim Hrisoulas which lays things out clearly (re-printed with permission):

When you fuller a blade you do several things:

1: You lighten it by using less material, as the act of forging in the fuller actually widens the blade, so you use less material than you would if you forged an unfullered blade. (In stock removal the blade would also be lighter, as you would be removing the material instead of leaving it there).

2: You stiffen the blade. In an unfullered blade, you only have a "single" center spine. This is especially true in terms of the flattened diamond cross section common to most unfullered double- edged blades. This cross section would be rather "whippy" on a blade that is close to three feet long. Fullering produces two "spines" on the blade, one on each side of the fuller where the edge bevels come in contact with the fuller. This stiffens the blade, and the difference between a non-fullered blade and a fullered one is quite remarkable.

Fullers on knives do the same thing, although on a smaller blade the effects are not as easily seen or felt. Actually looking at fullers from an engineering point of view they really are a sophisticated forging technique, and it was the fullered swordblade that pointed the way to modern "I" beam construction.

When combined with proper distal tapers, proper heat treating and tempering, a fullered blade will, without a doubt, be anywhere from 20% to 35% lighter than a non-fullered blade without any sacrifice of strength or blade integrity.

Fullers were not "blood grooves" or there to "break the suction" or for some other grisly purpose. They served a very important structural function. That's all. I have spent the last 27 years studying this and I can prove it beyond any doubt...

Source: rec.knives Newsgroup May 1998
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afishhunter said:
Back in the day blood grooves were used to help prevent "stiction" on the battlefield when the blade was withdrawn. Supposedly it allowed some air in, reducing the suction created by the blood when the blade was pulled out.
Click to expand...

Ths is the "myth" of which my father spoke. He never saw any value in the blood groove.

Captain O
 
Some very good answers here. Meanwhile, this could lead to a similar discussion on the grooves in the sides of a Japanese santoku kitchen knife. It is claimed that they allow the easier release of cut vegetables such as potato slices. My santoku does not have the grooves; a friend's does have the grooves, and he claims they are helpful.
 
Very interesting and informative thread about a subject I'd never even heard of! :thumbup::thumbup:
But the thread is seriously deficient in photos/diagrams, IMHO! :(

- GT
 
5K Qs said:
Very interesting and informative thread about a subject I'd never even heard of! :thumbup::thumbup:
But the thread is seriously deficient in photos/diagrams, IMHO! :(

- GT
Click to expand...

Here ya go;

Camillus Mark 2
CamillusMk2annotated_zpsxtl4ygqr.jpg


Camillus Pilot Survival Knives
psk6003annotated_zpsuzbs5yn8.jpg
 
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afishhunter said:
Back in the day blood grooves were used to help prevent "stiction" on the battlefield when the blade was withdrawn. Supposedly it allowed some air in, reducing the suction created by the blood when the blade was pulled out.
Click to expand...

Is this really a myth ? .slender blades and most Daggers don't have them . slashing blades sutch as the cavalry swords don't have the them . back in the day their were put on large thick stabing weapons . I don't think this was for looks or whight maybe this is one for the mythbusters :D
 
I don't particularly like the term "blood grooves," It lends credence to those that would call anything with a blade a weapon. As to your question, fullers were invented by the Vikings to lighten swords without lowering the dimensions of the blade. As others have pointed out, this was the original I-beam. That said, fullers do not benefit a knife under 8, 9, 10 inches or so for reasons Macchina pointed out:
Macchina said:
The thing about I-beams is that they are designed to be strong in one axis only. The upper and lower flanges on an I-beam are loaded in compression (the flange on the inside of the bend) and tension (the flange on the outside of the bend) and the web is put into torsion (internal shear) between the flanges trying to resist the growing/shrinking of the flanges as they are loaded...If a blade with a fuller makes a rudimentary I-beam then the blade would theoretically be stronger (per pound) with forces parallel to the blades (cutting/chopping) but weaker in side-loading.
Click to expand...

These days, fullers are used frequently in folding knives for aesthetic reasons. The only possible benefit is to alleviate negative pressure when cutting things like a peach so that the peach slice will not stick to the blade as you pull it away. All said and done, if you are considering purchasing a knife with fullers, don't let the fact that they serve no purpose stop you. Do what you love :)
 
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