| 1. Preparation of materials |
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steel / carbon steel for cutlery " Aogami #2 " or " Aogami
Super " steel
(steel is iron with a high carbon content)
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iron / soft iron for cutlery (iron with a low carbon content)
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The iron strip is split into two, and the steel strip is put between the two layers of iron. The layers are then sealed. Afterwards, the steel/iron strip is heated to the lowest temperature that steel and iron can bond together (about 900℃ ).
The next step is to keep beating the metal and hand-forge the layers into one.
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| " iron splitting " |
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" putting steel between iron" |
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We lengthen the "triple-structure-forged" metal into a long,
narrow rod. Then we heat it until it is soft and red, and cut it into the
specific size using a cold chisel and hammer. |
| " lengthen long and narrow " |
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We lengthen the "triple-structure-forged" metal into a long,
narrow rod. Then we heat it until it is soft and red, and cut it into the
specific size using a cold When you think of a "blacksmith",
the image of a man "forging over fire" probably comes to your
mind. We heat and forge the materials 3 or 4 times to prevent decarbonation
which can result in loss of strength, and then shape the form with a hammer
as quickly as possible. A bladesmith can forge 3 knives at the same time.
Seeing red hot molten metal suddenly being malleable is quite fascinating
and mysterious. Nevertheless, it is a really difficult and hot task, especially
in the summer, even it is performed outdoors where there is a breeze. The
heat can radiate over quite a large area. and hammer. |
| " cutting edge forging " |
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" handle inserting part forging " |
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After heating the metal to 760 〜 800 ℃, we put it into "straw ashes" to cool off gradually for a whole day and night. This ensures that the integrity of the metal is kept.
By slowly cooling the metal, we can continue to carry out following processes such as "Taking form" and "Shaping" without worrying about any unrelieved stress on the metal.
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| " annealing " |
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after " annealing " |
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The bladesmith puts a template over the forged metal, traces the shape
using a tool called "marking bar", and then trims out the knife
using a tool called "handshire". |
| " tracing " |
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" cutting " |
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Here we impress the family seal "源盛高"(Minamotonomoritaka)
onto the blade. |
| " seal stamping " |
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Lightly straighten out any distortion and remove minor blemishes. |
| " straightening out " |
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Shape the final form of the knife using a grinder. Afterwards we polish
the surface with a big wet rolling whetstone, called a "water grinder". |
| " shaping form with a grinder " |
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| 10. Hardening (Quenching) |
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We harden the knife with 2 methods, "water hardening" and "oil hardening".
We heat the knives to the ideal temperature of 790 〜 830 ℃ slowly and evenly. After that, we cool them in water or oil. At this stage, the steel structure becomes dense and very hard. The temperature control of the "Hardening" process requires a lot of experience and intuition because the temperature is determined by the color of the hot metal. "Hardening" is said to be a "真剣勝負" (serious fight) because if we miss the timing, we fail, and the knife will be useless.
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The steel becomes very hard after the "Hardening" process, but
it also becomes brittle and the edge can be nicked easily. To achieve better
edge retention, we then temper the knives for 30 〜 60 minutes at 160 〜
230 ℃. |
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| 12. Removal of distortions |
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Metal can expand and shrink during the heating and cooling processes. After
"Hardening" and "Tempering", knives will become distorted.
Therefore we carefully correct the distortions with a special hammer. |
| "removal of distortion " |
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" leveling off " |
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Throughout the grinding process, we use the "water grinder" at room temperature.
In the winter, it can be quite hard a work as the water becomes freezing cold. At the first stage of the grinding, we roughly grind off the iron on both sides of the blade to expose the hard steel in the center.
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| " rough grinding " |
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For the second stage of grinding, we use a finer whetstone to smoothen
the surface and the line between the two metals. We then polish and buff
the metal to sheen.
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| " smooth grinding " |
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| 15. Final grinding and sharpening |
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To finish off, we use the finest whetstone and sharpen the edge by hand.
We also test the blade by cutting papers to ensure that the edge is razor
sharp.
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| " last grinding " |
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" sharpness testing " |
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| 16. Handle fitting - Preservative treatment |
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To fit the handle, first we heat the tang slightly to make it flexible.
Then the handle is wiggled into position and glued into place. Finally,
we remove any remaining stains and rust-prove the knife. FINISH!
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| " handle fitting " |
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