What is purpose of fullers on blades?

kahnjar1 · 21st June 2016, 09:20 PM

Probably a very simple answer to this question, but can anyone tell me why some sword/knife blades have fullers and some do not.
Also what is the purpose of this? Various sources call these a "blood grove" but I have my doubts that this is the reason.
Stu

Timo Nieminen · 21st June 2016, 09:51 PM

Lightening/strengthening the blade, and/or ornament.

Ornament is obvious. Sometimes fullers are cut into blade to remove flaws.

Lightening and strengthening deserve a few more words. A blade is usually strong enough in the front-to-back direction, but side-to-side stiffness depends on tradeoff between weight and strength. Stiffness depends on the cube of the thickness, so a little bit more thickness can have a large effect on the stiffness. But thickness adds weight. So, enter fullers - a blade of the same thickness with fullers has a smaller cross-sectional area. There is less steel, so there is less weight. If the thickness of the blade is the same, the fullered blade is almost as stiff as the unfullered.

How to make a blade lighter with a fuller: take a blade, and cut a fuller into it. You remove steel, and the blade is lighter. You only reduce the stiffness by a small amount.

How to make a blade stiffer (i.e., stronger): when forging the blade, forge the fuller. You have the same amount of steel, and if you make the blade the same width, it will be thicker. The weight is the same, and the stiffness is greater.

The usual analogy is the I-beam - not as stiff as a solid beam, but a much higher stiffness-to-weight ratio.

Some people will claim that cutting a fuller into a blade makes it stronger. No, it makes it weaker. Forging a fuller can make a blade stronger.

The same kind of weight/stiffness benefits can be obtained from hollow-grinds, T-spines, raised ridges, Z-section blades, etc.

Some martial arts people like fullers because a fullered blade makes more noise when they swing. The noise is sensitive to blade alignment and speed, so it's useful audio feedback.

ariel · 21st June 2016, 09:55 PM

AFAIK, just to decrease the weight without compromising stiffness.

I have heard opinions that they actually increased blade stiffness by approximating profile of the blade to the I-type configuration, but several engineering souls said that it was nonsense, and that stiffness actually decreases but not by much.

Beyond that I am totally ignorant: math was never my strong suit:-)

ariel · 21st June 2016, 09:58 PM

Ooops....
You were too fast , or I was too slow:-)

But I am glad I was able to transmit the wisdom of the professionals without major errors:-)

Oliver Pinchot · 21st June 2016, 10:10 PM

Strictly speaking, a fuller is a depression which is forged into the blade with a fullering tool. Anything cut or ground into the blade following rough forging by mechanical means is called a groove.

ariel · 22nd June 2016, 03:12 AM

That's new to me!
So fullers are in fact better than grooves?
Thanks Oliver!

kahnjar1 · 22nd June 2016, 05:27 AM

Thanks for info so far, but I am still not sure WHY they are there. Most European (military) swords do not have them and do not seem to suffer from either weakness of heaviness. So the question really remains as to what purpose they serve.
Stu

Roland_M · 22nd June 2016, 01:13 PM

The groove makes the sword lighter (faster and better to handle) and also allows control about the mass distribution, used to adjust the inertia and gravity (point of balance) of the sword.

motan · 22nd June 2016, 01:57 PM

This is not a very educated answer, just logical guesses.
As some of you mentioned before, weight distribution and especially reducing weight while keeping stiffness and size intact make lots of sense. Steel beams and construction elements in modern use are never a solid bar, but have I, H or hollow pipe shape for the same reasons.
The second possible reason is related to the "blood groove". A straight stab may make a dagger or sword hard to pull out because of the suction forces. Fullers could make a weapon easier to extract. In a way, like some modern chef knives have depressions on the blade to prevent vegetables from sticking to the blade by suction.
But like many other features of weapons, function has become fashion and individual cases would be hard to explain because the functional aspect may no longer be relevant. For example, the central ridge construction has been carried over from bronze to steel weapons, where, at least in some cases, are not necessary anymore.

fernando · 22nd June 2016, 02:55 PM

Sorry to come up with a recurrent source:

https://en.wikipedia.org/wiki/Fuller_(weapon)

This because in my home language we mainly (only) use the term 'goteira' (from the Latin gutta =drop ) as for blood dripping, although we (some) are aware this is a fantasy.
It would however be interesting to know how such connotation was born ... semantic wise.

Roland_M · 22nd June 2016, 03:38 PM

Quote:

Originally Posted by fernando

Sorry to come up with a recurrent source:

https://en.wikipedia.org/wiki/Fuller_(weapon)

This because in my home language we mainly (only) use the term 'goteira' (from the Latin gutta =drop ) as for blood dripping, although we (some) are aware this is a fantasy.
It would however be interesting to know how such connotation was born ... semantic wise.

Hi Fernando,

it's the same in Germany. We call it blood groove (Blut-Rinne). I think this term was invented by civilians or maybe authors of adventure books about war. My own father is one of the people which really believe, that the groove was made to led the blood away from body with more efficiency or similar stupid stuff.

Roland

Battara · 22nd June 2016, 04:14 PM

Roland, this is so common among so many peoples around the world since the early 20th century, after the need for bladed weaponry was past.

thinreadline · 23rd June 2016, 11:08 AM

Quote:

Originally Posted by Roland_M

Hi Fernando,

it's the same in Germany. We call it blood groove (Blut-Rinne). I think this term was invented by civilians or maybe authors of adventure books about war. My own father is one of the people which really believe, that the groove was made to led the blood away from body with more efficiency or similar stupid stuff.

Roland

This is a commonly held belief especially amongst those who have been in the armed forces. It is usually a fantasy promulgated by macho training sergeants to young recruits to scare or impress them ... even I was told this in the 1970s by several NCOs when I was in the Joint Services .

Roland_M · 23rd June 2016, 12:14 PM

Quote:

Originally Posted by thinreadline

This is a commonly held belief especially amongst those who have been in the armed forces. It is usually a fantasy promulgated by macho training sergeants to young recruits to scare or impress them ... even I was told this in the 1970s by several NCOs when I was in the Joint Services .

Thank you for your explanation. Maybe this is a kind of training sergeant running gag and they always have tears in their eyes from laughing, if the recruits believe that.

My father told this to me when I was six or so and I couldnt believe that. I have been thinking about this for a long time as a child, to find out whats wrong with this theory.

thinreadline · 23rd June 2016, 11:05 AM

Quote:

Originally Posted by fernando

Sorry to come up with a recurrent source:

https://en.wikipedia.org/wiki/Fuller_(weapon)

This because in my home language we mainly (only) use the term 'goteira' (from the Latin gutta =drop ) as for blood dripping, although we (some) are aware this is a fantasy.
It would however be interesting to know how such connotation was born ... semantic wise.

But Fernando your word goteira and the English word gutter have the same Latin root ie 'gutta' ... and of course a fuller has the same appearance as a gutter but not necessarily the same function

21st June 2016, 09:20 PM	#1
kahnjar1 Member Join Date: Aug 2007 Location: CHRISTCHURCH NEW ZEALAND Posts: 2,731	What is purpose of fullers on blades? Probably a very simple answer to this question, but can anyone tell me why some sword/knife blades have fullers and some do not. Also what is the purpose of this? Various sources call these a "blood grove" but I have my doubts that this is the reason. Stu

22nd June 2016, 01:57 PM	#9
motan Member Join Date: Apr 2016 Location: Jerusalem Posts: 274	Why fullers? This is not a very educated answer, just logical guesses. As some of you mentioned before, weight distribution and especially reducing weight while keeping stiffness and size intact make lots of sense. Steel beams and construction elements in modern use are never a solid bar, but have I, H or hollow pipe shape for the same reasons. The second possible reason is related to the "blood groove". A straight stab may make a dagger or sword hard to pull out because of the suction forces. Fullers could make a weapon easier to extract. In a way, like some modern chef knives have depressions on the blade to prevent vegetables from sticking to the blade by suction. But like many other features of weapons, function has become fashion and individual cases would be hard to explain because the functional aspect may no longer be relevant. For example, the central ridge construction has been carried over from bronze to steel weapons, where, at least in some cases, are not necessary anymore.

21st June 2016, 09:51 PM	#2
Timo Nieminen Member Join Date: Mar 2012 Posts: 422	Lightening/strengthening the blade, and/or ornament. Ornament is obvious. Sometimes fullers are cut into blade to remove flaws. Lightening and strengthening deserve a few more words. A blade is usually strong enough in the front-to-back direction, but side-to-side stiffness depends on tradeoff between weight and strength. Stiffness depends on the cube of the thickness, so a little bit more thickness can have a large effect on the stiffness. But thickness adds weight. So, enter fullers - a blade of the same thickness with fullers has a smaller cross-sectional area. There is less steel, so there is less weight. If the thickness of the blade is the same, the fullered blade is almost as stiff as the unfullered. How to make a blade lighter with a fuller: take a blade, and cut a fuller into it. You remove steel, and the blade is lighter. You only reduce the stiffness by a small amount. How to make a blade stiffer (i.e., stronger): when forging the blade, forge the fuller. You have the same amount of steel, and if you make the blade the same width, it will be thicker. The weight is the same, and the stiffness is greater. The usual analogy is the I-beam - not as stiff as a solid beam, but a much higher stiffness-to-weight ratio. Some people will claim that cutting a fuller into a blade makes it stronger. No, it makes it weaker. Forging a fuller can make a blade stronger. The same kind of weight/stiffness benefits can be obtained from hollow-grinds, T-spines, raised ridges, Z-section blades, etc. Some martial arts people like fullers because a fullered blade makes more noise when they swing. The noise is sensitive to blade alignment and speed, so it's useful audio feedback.

21st June 2016, 09:55 PM	#3
ariel Member Join Date: Dec 2004 Location: Ann Arbor, MI Posts: 5,503	AFAIK, just to decrease the weight without compromising stiffness. I have heard opinions that they actually increased blade stiffness by approximating profile of the blade to the I-type configuration, but several engineering souls said that it was nonsense, and that stiffness actually decreases but not by much. Beyond that I am totally ignorant: math was never my strong suit:-)

21st June 2016, 09:58 PM	#4
ariel Member Join Date: Dec 2004 Location: Ann Arbor, MI Posts: 5,503	Ooops.... You were too fast , or I was too slow:-) But I am glad I was able to transmit the wisdom of the professionals without major errors:-)

21st June 2016, 10:10 PM	#5
Oliver Pinchot Member Join Date: Sep 2012 Posts: 456	Strictly speaking, a fuller is a depression which is forged into the blade with a fullering tool. Anything cut or ground into the blade following rough forging by mechanical means is called a groove.

22nd June 2016, 03:12 AM	#6
ariel Member Join Date: Dec 2004 Location: Ann Arbor, MI Posts: 5,503	That's new to me! So fullers are in fact better than grooves? Thanks Oliver!

22nd June 2016, 05:27 AM	#7
kahnjar1 Member Join Date: Aug 2007 Location: CHRISTCHURCH NEW ZEALAND Posts: 2,731	Thanks for info so far, but I am still not sure WHY they are there. Most European (military) swords do not have them and do not seem to suffer from either weakness of heaviness. So the question really remains as to what purpose they serve. Stu

22nd June 2016, 01:13 PM	#8
Roland_M Member Join Date: Aug 2014 Location: Germany Posts: 525	The groove makes the sword lighter (faster and better to handle) and also allows control about the mass distribution, used to adjust the inertia and gravity (point of balance) of the sword.

22nd June 2016, 02:55 PM	#10
fernando Lead Moderator European Armoury Join Date: Dec 2004 Location: Portugal Posts: 9,694	Sorry to come up with a recurrent source: https://en.wikipedia.org/wiki/Fuller_(weapon) This because in my home language we mainly (only) use the term 'goteira' (from the Latin gutta =drop ) as for blood dripping, although we (some) are aware this is a fantasy. It would however be interesting to know how such connotation was born ... semantic wise.

22nd June 2016, 04:14 PM	#12
Battara EAAF Staff Join Date: Dec 2004 Location: Louisville, KY Posts: 7,200	Roland, this is so common among so many peoples around the world since the early 20th century, after the need for bladed weaponry was past.