Shooting for 55-60 HRC file test. It's passing the hardness test, except maybe the one little blade edge spot in the middle of the dark spot on left. The 440C heat treat guidance I used was from Evenheat to 1850f 20 minutes, air quench to no less than 125f then temper at 220f 2 hours, air cool then final temper at 200f 2 hours.
Still wondering if I did something wrong or is this a metal flaw in the piece of 440C.
Thanks
Joel