Nata (屶, directly translated “mountain sword”, or 鉈) come in various sizes and shapes, but most fit the description of a light brush hatchet or heavy camp knife. Common characteristics include thick spines and heavy blades, often with single beveled edges similar to Japanese wood chisels. This type work well for medium duty camp tasks, carving hatchet work, roughing and shaping, green wood work, and bamboo splitting. Similar to boat builder’s or timber framer’s slicks, they can make controlled straight slices due to their mass and chisel-like bevel. Another common variation has double sided bevels, cord wrapped integral handles, and curved or hooked blades for working in the rice fields.
This article will not aim to document the standard methods of nata handle construction, but will cover some of the considerations for undertaking a nihonto-fusion style method of mounting. Nor will this be a complete tutorial format, but rather an overview of some of the important points for the successful engineering of a knife in this manner.
Most nata are permanently mounted to a hardwood handle because it is faster and easier for production. However, this piece has been assembled in the takedown style using elements of nihonto handle engineering and features swordsmith style hon-yaki edge hardening rather than a thin steel edge laminated to an iron body.
This style of nata has a straight edge and squared tip with a thick spine and a single beveled (kiriha-zukuri) edge similar to that of a Japanese wood chisel. The raw material in this case was exactly half of a reclaimed lawn mower blade, the tip next to the center hole and the worn-down former cutting edge area becoming the tang. When using lawn mower blades it is best to look for older ones as some of the new ones are made from air-hardening steel rather than simple carbon steel (this one was stamped “made in USA”).
When forging, the blade must be upset quite a bit from edge to spine to thicken the spine of the nata to about 1/4″ and reduce the depth of the blade to just under 2″. The volume of steel in this case produced a blade around 7″ long. The ura (back side of the blade, in this case towards a right-handed user’s left side) has a slightly (~1mm) concave shape forged into it for the purpose of flat sharpening, and the omote (front side, to the right of the user) bevel was forged in roughly and filed clean before hardening.
The tang tapers slightly but not as much as a tanto might and has a rectangular rather than triangular cross section. Standard style nata must have shorter tangs due to the method of slitting the handle right through, but in this case the tang will be hidden so longer is preferable, this one is at 3.25″ and still leaves plenty of room for the lanyard eye. There should be a shoulder at top and bottom so the ferrule can sit flush against the blade.
There are two approaches to the edge hardening, the standard and recommended one being to apply the clay mask an even distance from the edge on both sides, around 0.25″ or so (depth results will vary depending on the steel used). The goal is to form the hamon about halfway up the bevel on the omote side and the same distance on the ura, in a straight line (suguha). This should provide plenty of strength and support behind the hardened edge and make sharpening easier than with a fully through-hardened blade. If this approach is used, the blade can be sharpened on the ura or the omote.
In this case the clay was placed about 1/8″ from the edge on the omote and 0.5″ on the ura. This method creates a thinner hardened area on the bevel side but extends it farther up the flat side to prolong the sharpening life of the edge. Uneven clay application is a difficult technique as the uneven hamon pressure will bend the blade to one side (the omote), therefore the best approach if attempting this technique is to pre-bend the blade in the opposite direction so that it will be straight when hardened. If this approach is used, the blade is mostly sharpened on the omote and only slightly touched up on the ura.
A forged steel ferrule is absolutely necessary for this type of knife due to the strain placed on the handle. The ferrule should be at least 1/16″ thick and preferably 3/32″. It should fit snugly against the top and bottom of the tang, sitting tightly in the notches and taper slightly larger as it goes back (the tang will be tapering slightly smaller as it goes back). The profile can be round or slightly oval.
A tough hardwood block can be split and carved out to match the tang exactly and then glued back together before shaping the outside. The shoulder for the ferrule is carved first and then the handle shaped from it. The wood must fit exactly inside the ferrule as this intersection carries most of the force from the blade to the handle. When designing the handle, consider that the tang needs to have sufficient wood to the top and bottom to withstand the stress of chopping. In this case the handle is just over 5″ long. After shaping, the Sapele wood will be sanded smooth and coated with multiple thin wiped-on layers of natural urushi lacquer.
The mekugi hole through the handle should taper slightly and the back of the tang hole should align perfectly with it when fully seated. The peg should be carved from strong bamboo and fit as exactly as possible to the tapered hole. The outside of the bamboo is the strongest part and should face towards the back of the handle. When looking at the end grain it is the area with the most holes or “dots” on it. When tapering the mekugi the outside edge of the bamboo should not be removed at all so that the strong side of a finished mekugi has lines running from top to bottom.
See the full specs of this nata here: Available Work: Hon-Yaki Nata