Sakai Forged BladesPhoto：Osaka Prefecture

  • Metal works
  • Osaka

Sakai Forged Blades Sakai Uchihamono

Sakai Uchihamono is known for its exceptionally sharp and long-lasting cutting edge, created by forge-welding soft iron and steel, then shaping and sharpening the blade with highly skilled techniques. Specialized artisans divide the work of forging, sharpening, and handle fitting to produce knives for a wide range of uses. It was designated a Traditional Craft by the Japanese government in 1982.

Description

What is Sakai Forged Blades ?

Sakai Uchihamono are traditional forged blades, including kitchen knives and scissors, produced mainly in Sakai and Osaka City, Osaka Prefecture. On March 5, 1982, they were designated as a Traditional Craft by the Japanese government.
A defining characteristic of Sakai Uchihamono is the specialized division of labor among craftspeople responsible for forging, sharpening, and handle fitting.
Many traditional Japanese kitchen knives are made by forge-welding a hard carbon-steel cutting edge to a softer iron body. This combination provides a hard cutting edge together with a tougher supporting layer. Other knives, known as honyaki, are forged from a single piece of steel, so the construction and heat-treatment process varies according to the type of blade.
The blacksmith heats the metal in a forge and repeatedly hammers it into shape. The blade is then hardened and tempered to achieve the required balance of hardness and toughness.
A specialist sharpener subsequently uses a sequence of grinding stones to adjust the thickness, geometry, and cutting angle of the blade according to its intended purpose.
Finally, the handle is fitted and the balance and alignment of the completed knife are carefully checked.
Sakai has developed numerous specialized knife forms, including deba for preparing fish, usuba for vegetables, and long, narrow knives used for slicing sashimi. Scissors are also included within the nationally designated Sakai Uchihamono tradition.
The forging, heat-treatment, sharpening, and finishing skills developed over generations continue to be practiced today, particularly in the production of professional and traditional Japanese kitchen knives.

History

Sakai has a long history of metalworking.

Numerous large burial mounds were constructed in and around the area during the Kofun period, requiring large quantities of iron tools such as spades and hoes. This early metalworking activity forms part of the broader historical background of Sakai's later blacksmithing tradition.

During the sixteenth century, Sakai prospered as an important center of domestic and international trade. After firearms were introduced to Japan in 1543, firearms were also produced in Sakai, which became one of the country's important manufacturing centers during the Sengoku period.

Tobacco also reached Japan during the sixteenth century. By the Tensho era, from 1573 to 1592, specialized knives for finely cutting tobacco leaves were being produced in Sakai.

The quality of these tobacco knives earned a strong reputation. During the Edo period, the Tokugawa shogunate authorized the use of the Sakai Kiwame mark, helping establish the reputation of Sakai blades throughout Japan.

Production later expanded to kitchen knives, including deba and other specialized forms. By the late Edo period, scissors for flower arranging and gardening were also being made, and increasingly specialized groups of craftspeople developed within the production area.

With the mechanization of tobacco processing in the modern period, demand for tobacco knives declined. Sakai craftspeople instead applied their accumulated forging and sharpening skills increasingly to kitchen knives and other blades.

The specialized division of labor between blacksmiths, sharpeners, handle fitters, and related craftspeople also continued to develop.

On March 5, 1982, Sakai Uchihamono were designated as a Traditional Craft by the Japanese government.

Today, traditional forging, heat treatment, sharpening, and finishing techniques continue to be practiced in Sakai and Osaka City.

Production Process

  1. 1. Steel welding Steel coated with boric acid, borax, and iron oxide powder is stacked upon red heated soft iron and softened in a furnace at about 900ºC (about 1652℉). The two metals are hammered to bond and create a steel and iron plate for the base of a blade.
  2. 2. Shaping The flattened iron is reheated to about 600 to 700ºC (about 1112 to 1292℉) and hammered out repeatedly to thin the metal. The iron and steel are fused and the rough shape of the knife is created. Any excess metal is cut off and the tang (attachment) for the handle is also cut to its required shape.
  3. 3. Cooling down The shaped knife is set down on a bed of straw and left to naturally cool down. The slow cooling of the knife leading the straw to become ash helps remove internal distortions.
  4. 4. Rough hammering To flatten out hammer marks and tiny holes left from shaping, the room temperature blade is hammered. Rough hammering beats out impurities, tempers the blade, fixes any distortion, and creates a uniform thickness.
  5. 5. Cutting The knife is placed on a cutting template and all excess metal is cut off.
  6. 6. Grinding After fixing distortions, an engraving is made on the reverse side. Excess metal and rough edges caused by cutting are smoothed off, and the entire surface is refined with a grinder. The knife is also hammered to revise any distortion.
  7. 7. Mud coating The knife is coated with mud to prevent uneven heating and ensure quick and even cooling during tempering. First, any oil or remaining dirt is removed from the knife, then mud is applied, and the blade is left to dry near a furnace.
  8. 8. Tempering Rapid cooling changes the molecular constituency of metal by making it harder. The process is very basic as the knife is heated to 750 to 800ºC (about 1382 to 1472℉) and immediately plunged into cold water. The knife is heated again to 180 to 200ºC (about 356 to 392℉) and allowed to cool naturally which increases the blade's viscosity and strength and helps prevent chipping. To judge the right temperature and know when to stop heating, water is splashed onto the blade and the way the droplets run is watched by the craftsmen, who rely on training and experience.
  9. 9. Polishing Polishing turns good steel from a simple metal sheet into a knife. This process occurs in the following order of rough polishing, fine polishing, reverse side polishing, hazing, and then final polishing.
    Although named "rough", the rough polishing is an important process as it determines the angle of the blade edge. During this step, any visible distortion is diligently checked. Next, for fine polishing, the blade edge continues to be worked and any scratches and distortions resulting from rough polishing are polished, along with the adjustment of the blade thickness. In this stage as well, any distortion is checked. For reverse side polishing, the reverse of the blade is also lightly polished. By increasingly finer polishing, scratches are removed and any distortion is checked. During hazing, kneaded whetstone powder is rubbed on the knife blade, giving the iron a flat subdued color and shining the steel. This clear border between the iron and steel helps show off the beauty of the knife. The final polishing consists of a very fine whetstone used to carefully polish and finish the blade. With a razor edge of the highest quality, the blade is ready to be fitted with a handle.

Facility Information

Sakai Traditional Crafts Museum

Other Metal works

Other Crafts Made in Osaka