盛高刃物製造工程

　1. Materials

Steel / carbon steel for cutlery "Aogami #2" or "Aogami Super" Steel
(Steel is iron with a high carbon content.)

Iron / soft iron for cutlery (iron with a low carbon content)

　 2. Heating

The iron strip is split into two, and the steel strip is placed between the two layers of iron. The layers are then sealed. Afterwards, the steel/iron strip is heated to the lowest temperature at which steel and iron can bond together (about 900℃).

The next step is to keep beating the metal and hand-forging the layers into one.

Splitting the iron

Putting steel between iron

　3. Cutting

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 desired size using a cold chisel and hammer.

Lengthening the metal

　4. Forging over fire

We heat and forge the materials 3 or 4 times to prevent decarbonation which can result in loss of strength, and then shape the blade with a hammer as quickly as possible. A blacksmith can forge 3 knives at the same time.

Cutting edge forging

Tang forging

　5. Annealing

After heating the metal to 760 ～ 800 ℃, we put it into straw ash to cool off gradually for a whole day and night. This ensures that the integrity of the metal is maintained. By slowly cooling the metal, we can continue to carry out processes such as "Taking form" and "Shaping" without worrying about any unrelieved stress on the metal.

Annealing

After annealing

　6. Taking form

The blacksmith puts a template over the forged metal, traces the shape using a tool called a "marking bar" and then trims out the knife using a tool called a "handshire".

Tracing

Cutting

　7. Seal stamping

Here we impress the family seal "源盛高"(Minamotonomoritaka) onto the blade.

Seal stamping

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　8. Straightening

Lightly straighten out any distortions and remove minor blemishes.

Straightening

　9. Shaping

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

　10. Hardening (Quenching)

We harden the knife by 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.

　11. Tempering

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 ℃.

　12. Removal of distortions

Metal can expand and shrink during the heating and cooling processes. After hardening and tempering, the knives will become distorted. Therefore we carefully correct the distortions with a special hammer.

Removal of distortions

Leveling off

　13. Rough grinding

Throughout the grinding process, we use a water grinder at room temperature.

In the first stage of grinding, we roughly grind off the iron on both sides of the blade to expose the hard steel in the center.

Rough grinding

　14. Smooth grinding

In 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 blade.

Smooth grinding

　15. Final grinding and sharpening

To finish off, we use the finest whetstone and sharpen the edge by hand. We also test the blade by cutting paper to ensure that the edge is razor sharp.

Final grinding

Sharpness testing

　16. Handle fitting - Preservative treatment

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-proof the knife.

Success! The perfect knife.

Handle fitting