Knifemaking - Making a Tanto - Part 4 - Hardening and polishing

Sorry for the delay with videos. I had some problems. First blade cracked while quenching, so i had to make second one which also cracked. Then i made 3rd one, for which I used old leaf spring. Succesfully hardened it. Tried to go for hamon but unfortunately tempering oven went little bit too high with heat, and made the hamon not visible. I wanted to give a high polish to the blade, but in the end i decided that I'll go for machine finish with super fine scotch brite.

[@OKBushcraft]

Did you find out why the others cracked?
Did you anneal the steel before heat treatment?
I'm in the learning stage and am trying to see some of the do and do nots.

[@PKBladesmith]

+OKBushcraft
It was basically the fault of choosing the quench media. I used water which has really high cooling speed in martensitic transformation temperature range - this was the moment when blades cracked. I tried to combine cooling in water for 3-4 seconds and then changing to oil, but it seems that my lack of experience with plain carbon steels made me fail.

[@OKBushcraft]

+Piotr Kamiński
That's good to know.
I see people speak of oil hardening and water hardening steels but I don't know the difference between them yet.

[@PKBladesmith]

OKBushcraft Well, basically the "water hardening steels" are usually steels without any other additions different than carbon in large amounts. For example 1065, 1084, 1095, polish steels like N7E, N8E, japanese Shirogami, Aogami. Oil hardening steels usually have a chromium or manganese addition of 1% or more, like 52100, O1, O2, polish NC6. ŁH15, NZ3, 50HS/HF.

[@OKBushcraft]

+Piotr Kamiński
thanks for the info.