Tawm sez: "I'll disagree a bit with you Stan, I've made dies with thin O-1 parts
bolted to cold roll. Some dies use 1/4" inserts and punch out 4" dia. 16ga.
blanks. Also, I often harden rather big dies with a rosebud torch and a
bucket of quenching oil."

Right on. I have made lots of taps and even some threading dies from O-1 without formal heat treat
equipment.

Bob Swinney