All my puukkos have a Lauri’s special blades, which have very hard (62-63 HRC) cutting edge while the back is softer (normalized 34 HRC or spring-hardened 50 HRC). The edge cuts wildly while the softer back prevents breaking off. It is a modern version of a traditional hardening of puukko blade. Instead of fire, we harden the edge with electricity (induction current). The hardened zone is about 5-7 mm wide. We use 80CrV2 steel, which is like carbon steel, but small amounts of Chromium and Vanadium makes the heat treatment easier. I have selected the steel grade and developed the hardening process with Lauri.