Japanese ‘Chisel’ or nomi (鑿, のみ)
What is The Nomi Chisel is for?
The Nomi is a Japanese tool that western woodworkers would call a chisel. The Japanese chisel is not the same in every way to a western chisel. Like western chisels, the Nomi is made in many patterns to suit different woodworking tasks.
Almost every task you would use a chisel for in the west the Nomi is also used for in the East. The joints and projects may be different but the basic purpose of a chisel is to peel or chip away wood.
What is Different About the Japanese Chisel?
We already know the Nomi and western chisels have similarities but those are only superficial. The Japanese chisel has a number of differences such as:
- Blue or White Steel
- Hollow ground back
- Blade length
- Bevels angles
Traditionally the Japanese chisel is made from low carbon steel stock. Because this steel is softer than High-Speed Steel or Chrome Vanadium it can absorb shock better.
- 30° is good for softwood carpentry
- 35° is considered good for hardwood such as Oak
In comparison to western chisel, sharpening angles the Japanese chisel or Nomi has a less acute angle for instance I sharpen my European chisels to 28° and 30° retrospectively.
But you may ask why is Japanese tool steel so hard?
Japanese steel is case hardened with Carbon at the cutting edge and tempered. White paper steel contains about 1.22% it is still mainly basic IRON.
Is Japanese Steel Brittle?
I own several Nomi tools and they are Brittle at the edge. Although they do sharpen to a very keen edge I do have to be careful not to damage it.
Japanese chisel sharpening
Sharpening hollow backed Japanese chisels must not be done in the same way as the Western chisel. The hollow back must be considered because you can over grind and damage your chisel by removing too much of the cutting edge.
Before you touch your cutting edge you must first flatten the back of your chisel. Using just a perfectly flat steel place the back of the chisel down and make repeated strokes.
Inspect the chisel and you will see polished and unpolished areas. If the back is not polished all over the contact area the back of your chisel needs flattening.
Because you do not want to remove excess material the cutting edge might need dressing. To dress the edge first you have to peen the edge. Using a small anvil and a small peening hammer lightly strike the back edge on the bevel so as to manipulate the tool steel of the chisel. Basically this will slowly bend the steel so that the edge is in line with the back of the chisel.
Once the back is is Flat
You can now sharpen the chisel, but wait doesn’t just grab your oil stone! An oil stone is no good for sharpening Japanese tool steel. You must use Waterstones for sharpening any Japanese tool steel such as the Nomi.
Check out our sharpening tutorial for more information on how to sharpen a Japanese Chisel.
The Steel Ferrule
Unlike most common European chisels the Nomi has a steel ferrule fitted.
What is the steel Ferrule for? The steel ferrule fitted to a chisel prevents the chisel handle from splitting. You should impact your chisel with a mallet but it is not unusual to see a chisel impacted with a hammer or a Japanese Genno.
The Genno will damage the handle of a Nomi and the handle above the ferrule will mushroom. You can easily repair the impact area by
- tap the ferrule or ring further down the handle.
- Soak the handle in Water
- Peen the end of the handle to secure the ferrule
Japanese Chisel Brands
These are the more recognised brand names for Japanese chisels
There are many more tool makers of the Nomi but the above is widely renown for different reasons. More obscure manufacturers make tools which are designed for a particular purpose.
Is a Japanese tool better than a Western tool?
I wouldn’t say that one is better than the other but that Japanese chisels are just different. They require different techniques for different projects in different cultures.