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Rustybolt
08-24-2011, 03:44 PM
What's the fuller for?

I contend that it adds strength while saving weight.


But then I could be full of sh*t.

lazlo
08-24-2011, 05:26 PM
In the old days, when bladesmiths believed in grain packing, a fuller, which was traditionally forged-in, was believed to stiffen the blade while reducing weight.
That's true, if you don't austentize (heat treat) the blade after you forge the fuller. Unfortunately, that would mean that you don't harden the blade :)

You can find mention of "edge packing" in old bladesmithing books -- the idea that you can pack the grains on the blade edge.

Now that grain packing has been debunked by modern metallurgist and bladesmiths, the fuller is primarily decorative and/or for lightening the blade in key areas.
Katanas often have bo-hi -- grooves that run along the spine. These are specifically to lighten the blade, although they also make a really cool whistling sound when you swing the sword :)

Kevin Cashen, ABS Master Smith and master metallurgist, has a great write-up here:


http://cashenblades.com/images/articles/lowdown.html

Going back to the aforementioned laws of conservation, it is fundamental that while matter can neither be created nor destroyed, it can be rearranged. While so many of the bladesmith's fantasies are physically impossible, hammering steel can have its effects all the same by rearranging things in very profound ways. How conditions now drastically change from anything like a fruit stand is that oranges can be squeezed, metal atoms cannot. The atomic stacking of steel, within the context of this article, cannot be condensed tighter, and that is why forging works the way it does. A ball of clay is much softer than steel, but they deform in a similar fashion. If we place that clay in a cylinder and bring a tight sealed piston to bear upon it, no amount of force we could muster would force the piston down beyond the mass of our soft clay. Why should we imagine our stronger steel to be any different? But this stubbornness about being squeezed is a good thing for the process of forging. Be it clay or steel, if we pinch it in one direction it will expand in another; this is how forging steel works and why "packing" steel cannot. If we are going to change the shape of steel we must find a way more in accordance with reality than compacting iron atoms. If we can't get those atoms to squeeze a little closer to accommodate our fantasies, perhaps we can get them to move around each other to achieve our goals, and that is what we will now examine.

boslab
08-24-2011, 11:27 PM
debunked or not steel is not homogeneous, during solidification 1/2 layers of atoms get jammed between full layers [aka dislocations] during processing [cold] these pile up and provide the energy for recrystalisation [annealing/normalising etc etc], also steel goes through volumetric changes such as found in peritectic transformations [bcc structure and fcc structure volumetric difference, noticable as a shrink in volume as it cools, does this not curve a katana? apparently it is or i was told it was by a japanese metallurgist but i may have got him wrong, i dont make knives or swords!]
were finding things out about metallurgy all the time, what of the siemens martin process of applying pressure to steel? or is this in a different context.
i think i would like a go at a knife though, given the prices for tidy ones at our local hunting shop, even basic ones cost a fortune!
regards
mark

lazlo
08-24-2011, 11:41 PM
steel goes through volumetric changes such as found in peritectic transformations [bcc structure and fcc structure volumetric difference, noticable as a shrink in volume as it cools, does this not curve a katana?

That's absolutely right Mark -- when you first plunge the katana blade into water it bends downward (wrong-ways) because the martensite forms on the thin, uninsulated edge first, and then it bends the other direction about 4 seconds later as the pearlite forms in the clay insulated spine. But that's not grain packing.

Grain packing was an old Wive's tale that you could pack the iron grains through forging. The edge packing variant was similar -- the old smiths would hammer cross-hatches on the edge, thinking it would compress the grains.

Forging aligns the grain, but you can't compress it. And in the case of the blade fuller, although you can align the grain along the fuller with a guillotine tool, once you austentize the blade to heat treat it, all that grain structure goes back into solution.

TGTool
08-24-2011, 11:41 PM
Not quite the same thing as the packing question, but years ago I was reading about agricultural tool practice somewhere in Eastern Europe (Hungary, Romania?). Hay, and I presume other crops, were cut with scythes and sickles which would require sharpening during the day in the fields. They didn't use stones for sharpening, but a small hammer and anvil or buck. I always wondered about that though I've never tried it on mine since files and stones are so handy. I presume it was metal thinning and wondered if it produced any work hardening as well. No telling what steel alloys would have been but a manganese steel, intentionally or unintentionally produced, might not have been out of the question.

sasquatch
08-25-2011, 12:09 AM
Can,t add any technical info to this, except as questioned, yes Sythes are still hammered to sharpen them, usually i,m guessing by people competeing in sytheing contests which seem to be becomming a big thing in certain areas.

HWooldridge
08-25-2011, 04:57 PM
The "packing" practice may have come into existence before blast furnace steel was available, when high carbon was typically made from carbonized wrought iron. Any WI that needed to be folded and welded would have benefited from extra hammering to homogenize the material. I am not suggesting this occurs at the atomic level but because WI is a mixture and not a solution like steel.

I've also read that "packing" is supposed to break up carbide formations but that may be a stretch because proper heat treat practices would have more benefit. In addition, hammering below critical temp can induce stresses, which is why I think some of the Japanese knife makers flip the blade back and forth in an attempt to equalize that stress and prevent side-to-side warpage.

tdmidget
08-25-2011, 05:11 PM
The "packing" practice may have come into existence before blast furnace steel was available, when high carbon was typically made from carbonized wrought iron.

Blast furnaces do not make steel. They make pig iron which is the feedstock for the production of steel and cast irons. The steel production is done in Bessemer converters, open hearth furnaces, or electric arc furnaces. Back in the day it would likely me made a piece at a time by the man who used it.

boslab
08-25-2011, 07:46 PM
That's absolutely right Mark -- when you first plunge the katana blade into water it bends downward (wrong-ways) because the martensite forms on the thin, uninsulated edge first, and then it bends the other direction about 4 seconds later as the pearlite forms in the clay insulated spine. But that's not grain packing.

Grain packing was an old Wive's tale that you could pack the iron grains through forging. The edge packing variant was similar -- the old smiths would hammer cross-hatches on the edge, thinking it would compress the grains.

Forging aligns the grain, but you can't compress it. And in the case of the blade fuller, although you can align the grain along the fuller with a guillotine tool, once you austentize the blade to heat treat it, all that grain structure goes back into solution.
i stand corrected, or educated, my thanks
regards
mark

HWooldridge
08-25-2011, 07:58 PM
Blast furnaces do not make steel. They make pig iron which is the feedstock for the production of steel and cast irons. The steel production is done in Bessemer converters, open hearth furnaces, or electric arc furnaces. Back in the day it would likely me made a piece at a time by the man who used it.

Maybe I should have written, "mass produced steel"...my point was to reference when steel was made using WI as the core material.

lazlo
08-25-2011, 09:30 PM
Hollis is talking about blister steel -- you take iron bars, pack carburize them individually, which leaves a skin ("blister") with super high carbon, forge-weld multiple bars together, and then repeatedly fold the resulting steel to homogenize the carbon content.

That's a good point -- that may be the source of the original grain packing story...