Japanese chisels (Nomi)
Japanese chisels (Nomi)
EXPERT KNOWLEDGE JAPANESE CHISELS (NOMI)
Whether you are finishing wood joints, re-piercing fits, contours or chamfers - the result of the work depends largely on the quality and sharpness of the Paring chisels. It must hold its edge, be easy to sharpen and easy to guide.
Blade made from two layers of steel
The Hardness cutting layer is fire-welded with soft iron, which protects the blade from brittle fracture and cushions the blow. (Hand forged under high temperatures). Advantage = Exceptional cutting steels with the highest possible hardness 62-63 HRC.
Hollow ground joint
The hollow grinding (Ura) on the mirror side reduces the contact surface and thus minimises friction. It also makes honing easier, as only the edge of the hardness cladding steel is machined. The hollow grinding is deeper towards the back, so it is always retained even when resharpening. (see graphic)
Angled blade
The angled blade increases the working depth to almost twice the blade length and thus achieves the working depth of Western chisels. The short blade enables precise guidance.
Matériau du manche features of Japanese chisels:
- Handles made from impact-resistant hardwoods
- Solid steel ring at the transition from the handle to the iron for maximum power transmission
- Strong steel ferrules, designed for efficient driving with the iron hammer
Production steps of Japanese chisels (hand-forged Production)
Japanese chisels are hand-forged. White or blue paper steel, a carbon steel with excellent cutting properties, is often used for the cutting layer. The basic steps in production are carried out by a manufacturer (e.g. Ioroi) as well as a master blacksmith such as Tasai.
- Fire welding of soft and hardness steel
- Forging of neck and tang
- Moulding of the blade
- Rough grinding, Hardness, Tempering
- Dressing the blade
- Final sharpening
- Shaping the handle from oak wood (usually Japanese white oak or red oak)
- Mounting
Japanese chisel, Production by hand in numerous intermediate steps.
Japanese chisel - The mirror surface (URA)
The mirror surface of Japanese chisels is unique in several respects. As the iron is constructed in two layers, the hardness of the cutting steel is found on the mirror surface and thus on the front part of the bevel. With western chisels, the mirror side is polished over the entire surface (approx. 90 mm) during sharpening. However, this has the disadvantage that the entire surface must also have a high degree of flatness. If the surface is not flat, a sharp cutting edge cannot be formed.
The flatness of the mirror surface depends on how flat the grinding stones are and how evenly the pressure is applied to the iron during sharpening. Both of these factors can only be improved with a lot of time and practice. A shorter mirror surface or a smaller surface in general is much easier to grind flat. This is where the Japanese design comes in. Instead of creating a large mirror side, the surface to be ground is reduced to the front area on the cutting edge (for edge formation) and the side areas (for support) by means of a hollow grind. The aim of the blacksmith and the user is to minimise the area between the front edge of the cutting edge and the hollow ground edge.
The smaller the surface, the more even it becomes during sharpening. As a result, the flattest surface shapes the best cutting edge. To ensure that the hollow grind does not disappear during resharpening, it becomes deeper towards the end of the blade. This means that the hollow retains its outer shape and does not disappear due to the regular honing of the mirror surface after sharpening. The prerequisite for this is that the hollow grinding is cleanly applied by the blacksmith.
Purpose of multiple use for Japanese chisels:
Some Japanese chisels have a multiple use on the mirror side. This creates additional ridges that make it easier to rest the chisel on wide tools.
Japanese chisels - Types
Oire Nomi
The Oire Nomi is the universal chisel that is driven with a hammer. Available in widths from 3 mm - 43 mm.
Atsu Nomi
Larger Shape of the Oire Nomi above. It is favoured by carpenters. 12, 15, 18 and 24 mm are available.
Mukomachi Nomi
The Japanese Mortise chisels, which is used for the Production of small mortises. 15, 18 and 24 mm are frequently used.
Uso Nomi / Shinogi Nomi
Paring chisels with a triangular, forged cross-section and usually longer handles. It is only used by hand and is used for re-piercing wooden joints. Common widths are between 6 mm and 30 mm.
Mori Nomi and Sokzarai Nomi
These two irons are used for Japanese sliding door construction. The shapes are very special and are most similar in cross-section to a cow's foot, to a crowbar.
FAQ about Japanese chisels
Why are Japanese chisels not ready to use?
With the exception of some series, Japanese chisels are not ready to use when purchased. The reason for this lies in the Japanese tradition. A tool manufacturer provides the worker with a tool of the best possible quality. To be able to work properly with the tool, the user himself must familiarise himself with its design and function. This "familiarisation" with the tool comes about through preparation before the user actually uses it. Got to tools in Japan are not produced by a tool manufacturer but by a blacksmith. The blacksmith's craft involves the Production of the chisel blade. The handle and assembly of the tool are of secondary importance to the blacksmith. For this reason, the clamps on Japanese chisels are generally not pre-assembled. Instructions for use explaining the work steps can be found with every tool supplied.
How is the ferrule mounted on Japanese chisels?
- Place the side with the larger inner diameter on the handle.
- Drive the ferrule onto the handle with a hammer. The handle should protrude the ferrule by approx. 3 mm. If the ferrule cannot be driven on, either remove Material all round the handle with a file or use a hammer to compress the handle in the area where the ferrule is driven on.
- The protruding part of the handle can now be immersed in water to soften the fibre. The wood can then be bent (shaped into a mushroom) by hitting the edge of the wood all around.
Why are the Japanese chisels black?
Tonoko Nuri technique according to Akio Tasai:
In this process in chisel production, a liquid mixture of alumina and carbon powder is applied to the ground iron. This layer enables a constant temperature on all parts of the blade during tempering and also ensures the formation of an even, black oxide layer to protect against rust.
