JAPANESE CHISEL (NOMI) BASICS
Understanding how chisels are constructed and their specific purposes will help you decide which chisel will best suit your woodworking needs. Here are some Chisel Basics.
CONSTRUCTION
Most Japanese Woodworking Chisels are handmade or drop forged and constructed in one of two ways. Most are made with a tang – a metal extension that fits up inside the handle. These Tang Chisels may or may not have a metal ring to reinforce the area where the tang enters the handle. In Socket Chisel construction, the tang is replaced with a cone that fits into the handle and is tightly mated (fitted) and held into place by friction.
BLADE STEELS
Unlike Western-style Chisels made from a single steel, Japanese Chisels are made of at least two steels. Most Japanese Chisels combine a bottom layer of sharp-edged White Paper Steel or Blue Paper Steel that has been heat- treated in the forge to an HRC64-66 hardness with a top layer of softer steel such as wrought iron. This hard/soft steel composition gives the tool a hard, durable cutting edge with shock resistance and the added strength of the second steel. White Paper Steel is more typically used than Blue Paper Steel. Although it is more brittle than Blue Paper Steel, White Paper Steel is thought to create a sharper edge. On the other hand, a Blue Paper Chisel will have tungsten and chromium added, which makes a blade that holds its edge longer and is a little more durable.
LEFT: This Damascus pattern is often seen on Japanese Chisels hand-forged by Master Blacksmiths. The blade area shows the many layers of forged steel, including the hard steel underneath that makes the cutting edge. CENTER: Much attention is given to the choice wood for chisel handles, as well as the look of the hoops. RIGHT: This is a good example of a multi-hollowed chisel back common to Japanese Chisels.
BACKS
For a chisel to be most effective, the back of the blade must be flat. Western chisels are always almost completely flat, but Japanese Chisels often have hollow ground areas to make sharpening easier. The hollowing leaves less of the extremely hard steel in the bottom layer to be
removed.
removed.
HANDLES AND HOOPS
Most Japanese Chisels have wooden handles, typically White or Red Oak, Ebony, Sandalwood or Boxwood. If a Japanese Chisel has a hoop, ring or ferrule (sagariwa) on top of the handle it can be struck with a mallet. If no hoop is present, the chisel is intended to be pushed by hand (not struck) and usually has a longer handle to facilitate this type of use. The Japanese believe the hoop helps to prevent the wooden handle from splitting during use.TYPES OF CHISELS AND THEIR BLADE SHAPES
Japanese Chisels are made for specific tasks in woodworking, such as cleaning out an opening or getting close for cleaning out edges. To accommodate these uses, chisel blades have different shapes and angles. Some have square, flat sides, some have angled sides to a flat edge, and some taper to a complete edge see illustrations at below). Basic types of Japanese Chisels and their uses are described below.
• Oire Chisels - These are used for most shop tasks, are available in the widest variety of widths and typically have blade lengths between 2" and 3". Generally, they have thin blades and come with a top hoop so they can be struck. Oire Chisels include Bench Chisels and Butterfly Chisels (considered by many to be the original shape of the Oire Chisels).
• Atsu Chisels - Atsu Chisels resemble a Butt Chisel but are thicker and stronger. These are used by carpenters and cabinetry makers to make large joints. Blades are usually 1/2" to 2", but may be as narrow as 1/8" and as wide as 3-1/2". Firmer Chisels and Post and Beam Chisels are in this category.
• Mukomachi (Mortise) Chisels - These are Mortise Chisels meant for striking to make small mortises or grooves. The narrow blade has a neck the same thickness as the cutting edge, which gives the blade the extra strength necessary to cut deep. The blade’s cross section is rectangular in shape with a hollow back and slightly concave top and edges. This concavity reduces friction when withdrawing chips in a narrow mortise.
• Tsuki (Paring) Chisels and Slicks - Designed to be used with two hands, these push chisels are used for cleaning mortises and smoothing joints. The blades are sharpened at a low angle for easier paring. Saya or Scabbard Chisels are a specialized form of Tsuki Chisels.
• Kote (Crank Necked Paring) Chisels - Kote Chisels are push chisels, like Paring Chisels, but with an offset blade. They are used for cleaning out long joints, such as housing joints or sliding dovetail
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