Quote:
Originally Posted by Marc M.
Correct, fullers make a blade lighter and stiffer. The lighter a blade is the faster you can move it and stiff enough that during that movement and under impact it doesn't go out of all directions.
Best regards
Marc
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Not lighter. Fullers (when properly made) are a hammered in feature. The metal isn't going anywhere. You compress it in one place; It swells out in another. That swelling can actually be seen in this piece to great effect. Notice the angle change as soon as the fuller stops. There is as much metal before fullering as there is immediately after.
It's not that they would have had to use more metal if not fullering either to get the same effect. Again there's differential heat treatment and tempering. to be clear tempering is hardening and heat treatment is softening. One usually heat treats/anneals a blade to work it, then tempers to harden it back up when work is completely. The amount of flexibility is determined by the temperature at which it is cooled from and the rate of cooling.
Now differential tempering and heat treatment is when the blade smith mentally divides the blade into quadrants. They carefully control the handling of each quadrant so that the blade has different properties of flexibility vs. hardness throughout it. Two quadrants is the easiest degree to do this to. You can temper up the whole blade. Then bring the upper quadrant back down a bit to make it more flexible without effecting the lower quadrant.
You can achieve this without fullering. So you don't need to have more metal to start with if you don't fuller. But it's just easier to fuller. Because if you give one part of the blade a lot more surface area than another. Then these quadrants are more physical than just lines you draw in your head about where you want the properties to change. Because an area of metal with a lot more surface area than another is going to respond differently to the same amount of heat and quench applied uniformly.
Fullering before tempering if done right should make it so that differential tempering and heat treatment isn't necessary. But even if you do it differentially anyway the fullering makes that easier to do without messing up. Because you really only get one or two shots at it when factoring in metal fatigue. Push it much further and you'll get cracks. So it's important to get it right.
It can be hard to imagine if you haven't done it or seen it done up close. It looks like they took metal way to make those grooves. But they really didn't. The metal just got moved around.