Gene has the filings for this one. He is correct that Higane and Jigane are two forms of steel used in making cutting edged blades. Higane is a very hard steel that sharpens to and generally holds a very sharp edge, Jigane on the other hand is a softer more flexible steel that is used as the body of blades. The two steels are married together to optimize the characteristics of both steel forms. A recent Woodwrights shop episode showed the WILLIAMSBURG blacksmith making a chisel by blending a hard steel cutting edge onto a soft body of steel. The welding of the steels together apparently is an historically old method and traceable through many cultures. Using the technique of creating a very hard edge on a resilient body allows a tool that will remain sharp while being struck, with the body of the tool absorbing the shock of the blow which might have fractured the sharp but brittle cutting edge, such as a chisel or an adze or froe.
DENNIS S: gets a grin award for the reference to his stress reactions
This puzzler was up for a longer time frame in hopes that there would be more response and or discussion. Maybe the next one?