I have been working on some knives im making from some old Nickelson files. Befor anyone gives me grief over not using known steel, I'm a collage student and can't afford any metal right now and I got the files for free. So here is what I did. I annealed them, shaped them, then normalized them, and quench them following the normal procedure for 1095. Heat to 1475 F and quench in oil. I have access to a hardness tester and the blades came out arround 68 HRC. All seems to be going well. But here is where I start to be confused.
I tempered them in my kitchen oven at 450 F, two one hour cycles. But the bladescame out blue instead of straw colored. So I tested them again and they were all arround 43 HRC. I don't understand how that happened. How did they get so soft? So i desided to re-quench the blades and did everything the same as before. But this time the blades came out of the quench between 35-45 HRC. What happened? Im going crazy trying to figure out why im getting these wierd results. First, why did my temper make theblades so soft? And second, why won't the blades get hard again?