Aisuki Knife

The Aisuki is a Japanese cutting tool used during the carving process of woodblock printmaking. The knife is unlike many modern designs with a pivot at the base of the handle.

The handle pivots to reveal a channel that holds a long thin piece of steel, chamfered at one end to create the cutting edge. The two parts of the handle are secured together with a ferrule; a folded piece of brass.

The opening design allows the blade to be resharpened and moved down the knife to maintain its comfortable position.

My design is based heavily on the traditional design shown here.

I modelled the handle in Fusion360 and chose the parameters for the size and taper of the section covered by the ferrule. I made two sketches of either end of the ferrule and then created a loft in the sheet metal tools. A flat pattern can then be created and a drawing can be printed:

The radius of each bend is governed by the sheet metal rules for 8mm brass.

This is the section of brass cut from the template, a triangular file is used to create v-grooves allowing the brass to be formed with a mallet.

The blade is made from 01 tool steel, the bevel was made with a file and then it was hardened over more than half of the length and tempered.

I 3D printed a prototype of the handle, which helped me to revise its shape and size. This also helped when creating the handle as I had a physical version to replicate which is much easier than working from drawings.

Here is the finished knife, I think it turned out really well. Incorporating Fusion360 in the design of the ferrule was really useful and I’m surprised how easy it was to create the flat pattern.