Hey Gimperfi,

I mentioned some of the fun you can have with differential hardening, so thought I'd share some pics. This started out as a dull old Nicholson file. I annealed it, then ground it, packed the spine with Satanite refractory clay, and hardened it, creating a differential temper (soft at the spine, super hard at the edge), as well as a hamon, the traditional Japanese visible hardening line. Thought maybe the pics would inspire you to upgrade your rig and get into heat treating. The clay coating: