Fuller'vit

Rick Marchand

Rick Marchand

Donkey on the Edge
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Jan 6, 2005
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Why do folks insist that adding a fuller to a blade strengthens it? ANY removal of material will make it weaker. Adding a fuller is just a crafty way to reduce weight while maintaining much of the structural integrity.

I just watched, yet another video where someone added a fuller to "stiffen" their blade. That hurts my mind.

I'll be okay... lol... rant over.
 
You hear the same thing with fluted barrels.

People don't understand the concept that a fluted bar is stronger than an unfluted bar of the same mass but with smaller exterior dimensions. No, a 2" square tube is not stiffer than a 2" square bar. Sorry. Math and everything. But a 2" square tube with 1/8" wall that's 4 feet long and weighs 12 lbs is much stiffer than a slightly less than 1" square bar that's 4 feet long and weighs the same 12 lbs.
 
I think some folks see a fuller as similar to using a bead roller to strengthen a piece of sheet metal. While they look similar from one side they are very different.
 
Exactly... a bead roller increases the cross section of the sheet metal, giving it rigidity/stiffness
 
.95" square bar, fixed at both ends, with a 500lb load in the center deflects over .100" - weighs 12.5 lbs
gkMXglk.jpg

2" x 2" square tube, fixed at both ends, with a 500lb load in the center deflects only .013" - weighs 12.5 lbs
cozmQZg.jpg

2" x 2" square bar, fixed at both ends, with a 500lb load in the center deflects .007" - but weighs 57 lbs.
KY0b3PV.jpg
 
This blade, fixed at the shoulder, 100lb of force at the tip
23tM3Fn.jpg


Same blade with a fuller
qlE8IDL.jpg


Didn't get stiffer.
 
I think he misconception comes from forging. If you are using say 1lbs of metal and you forge it into a knife with a fuller would it not be stiffer than the same 1 lbs of metal forged without the fuller?

But people transfer that over to stock removal blades. So nownthey have a 1 lbs blade without a fuller. They then grind away material to add that fuller. Now the knife is not as rigid as the 1lbs knife it started from.
 
What? If you forge in a fuller you're not compacting the metal in the fuller to a denser state. You're moving it out from around the fuller. The only way to have two forged blades of the same mass, one with a forged fuller and one without, is for them to be dimensionally different.
 
I heard it on FIF the other day when a judge stated that a fuller was to make the blade stiffer. I can live with this misrepresentation, because it isn't a fairy tale. It is just a case of apples to oranges.

The ones that really gets me going are that a fuller is properly called a blood groove because it:
A) makes the blade able to be removed ... because the vacuum will make it impossible to pull the blade out of a body.
and/or
B) makes the person bleed to death faster.
 
IMO, the misconception about making the blade stiffer is just as bad as the blood groove. They are both fairy tales.

... and no different than "edge packing" or quenching inline with magnetic North.
 
How about a reverse fuller? :p

Yep, cuts deflection in half! Be a trendsetter. Stiffen your blades with the reverse fullers, made from tubes, quenched in organic essential oils.

ygrC4Ts.jpg

ZQUxGKZ.jpg
 
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Pound for pound. A blade with the same weight and length without a fuller would be less stiff.
 
AVigil said:
Pound for pound. A blade with the same weight and length without a fuller would be less stiff.
Click to expand...

Maybe. If weight and length are constrained, where are you putting the extra material on the fullered knife?
 
It is not a matter of putting metal on a fullered knife, it is that a fullered blade that is the same length, width and the same weight will be stiffer then the unfullered blade of equal length, width and weight.


That is why they they put it their, it is not for looks.
 
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kuraki said:
What? If you forge in a fuller you're not compacting the metal in the fuller to a denser state. You're moving it out from around the fuller. The only way to have two forged blades of the same mass, one with a forged fuller and one without, is for them to be dimensionally different.
Click to expand...

Honestly I was just guessing I have no idea. But you have more experience it seems. So is what I said inaccurate? Taking 1 lbs of steel and forging it into a knife with a fuller so the resulting knife is 1lbs will not be stiffer than forging a knife where the result is 1lbs without a fuller?
 
Fullers were originally a place to GET material from. If you forge that area inward, the displaced mass goes outward, making the blade wider. That's all it ever was.
In the distant past, they just couldn't order a wider piece of steel from Fastenal.
They had to learn to work with what they had.
 
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