First attempt at making a knife

G

ghost squire

Joined
Feb 1, 2004
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Hello everybody, I am planning on making my first knife, a basic piece made from a file. I am planning on giving it a differential temper, and I have a pretty dumb question... When do I put the clay on, before hardening it and quenching it in brine, or before I put it in the oven to temper it? Also, after it develops the pale straw stuff during tempering, do I quench it or just leave it in the open air to cool?

Thanks for catering to a beginner like me!
 
You will apply the clay before quenching. The idea is to slow the cooling under the clay, resulting in a softer spine. I'd think twice about quenching a file in brine though. Maybe someone knows whether it's likely to be a water quench steel. Brine has a way of cracking blades which can be rather disconcerting after all the work to bring it to the quenching stage...
 
Awesome, that answers my question perfectly, thanks! On one website the recommended quenching medium for 1095 was brine, and I think the guy made Japanese swords with it. Browsing the general forums I have discovered that Japanese swords weren't actually tempered, hence the need for differential hardening... Are homogenously hardened, tempered steels superior? One would think that a bendy spine and body and a long lasting edge would be desireable.
 
Brine is often used when people want to bring out a distinct hamon, hense its use for Japanese blades. There are folks here with good experience quenching oil hardening steels in brine and might be able to give you some good pointers. But I'm not one of them. Risking a cracked blade just gives me the willies - I'm lazy and cheap and totally unwilling to throw away a bunch of my work. ;) Good luck and have fun.
 
You got some good advice already, but I want to clear something up real quick...

You said differential TEMPER but then talking about clay you were describing differential HARDENING. Two different things. They advised you on hardening, but differential tempering is done in a different way. You through harden the entire blade (no clay involved) and then give it a temper in your oven at the temp you want your edge to be. After it's done, you put the edge under water and with a torch heat the spine so it's tempered softer then the edge (usually a blue-purple color is typical). That will leave you with a hard edge and springy spine, similer to the diff hardening, but with no visible line and less risk of cracking.

There's other slightly different methods for diff temper, I just gave you mine.
 
Yes, avoid the water. Use a really fast oil like olive oil or Transmission fluid, and you should be ok.
 
My goal is for the hamon to be visible across the room :D

Will olive oil let that happen? Also, I am aiming for the edge to have an RC of 60-62, and I think oil quenching will lower that somewhat if I am not mistaken . Thanks for the advice, and lay some more on me!
 
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