Drawing the spine of a blade

[rodriguez7]

So, just to be on the safe side, I’ve been drawing the spine back on my blades in 15n20 knives, since I started making them, and I’ve been rather happy with their toughness. I’m putting the edge in a pan of water and using an oxy acetylene torch. My question is, what steels can I do this on? And is there certain steels I should avoid it on? I’ve heard of blue imbrittlement. Is it real? The steels I’m dabbling with right now, are 15n20, 8670, cruforge v, 80crv2, and I just ordered some w2. Those are steels I’m heat treating myself, or at least trying to. I’ve made some blades in 3v, 4v, cruwear, and 52100. but those were sent to peters for heat treat. The 52100 I used the torch on. I’m assuming those other 3 are plenty tough enough as is. I’ve never heard of anyone differentially hardening them.