Hello Mathew,

Just to let you know about the new location, I am going to move this thread to the more advanced discussion section as some of the aspects of you question could get deeper than heat treatment 101.

I'm done! I am sorry Mathew, but I just spent a good 30 minutes typing an in-depth answer to your question only to have the post page fail and lose it all. I want you to know that I tried, but I have things that can't wait in the shop. Sorry about that.

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I'm done! I am sorry Mathew, but I just spent a good 30 minutes typing an in-depth answer to your question only to have the post page fail and lose it all. I want you to know that I tried, but I have things that can't wait in the shop. Sorry about that.

Good morning Kevin,

I appreciate your efforts, especially as you sound busy. Hope you have far greater success in the workshop.

Best regards,

Matt

Kevin, The same thing happened to me yesterday.

Normally I type forum posts in MS Word and then past the finished draft into the forum box, this allows me to correct typos and gives me a backup copy should something like this happen, but I got in a rush to get to the shop.

Just thought I’d bump this, hoping someone can help me out... or link me to something. I’m more than happy to do the reading, just haven’t had much luck finding the relevant info in my own searches.

Thanks all.

I will try to start the conversation with what little knowledge and understanding I have.

There are a couple of questions about your question first. When you say "differential heat treatment" what are you referring to? Is it claying the blade for Hamon production, or is it simply edge quenching?

In the case of the first (claying) I do not use a lot of stainless steels, and the ones I do use are not suitable for Hamon because of the alloying. I am not a fan of edge quenching. I have an aversion to putting a hard phase transformation line in my blades.

I’m not sure where you got your info from, but it may have been based on the nature of simple steels. As Kevin has said many times, alloying changes everything. There is no real reason to edge quench or try claying for differential HT in a through hardening steel. These steels have been specifically designed to through harden, and deliberately changing that seems counterproductive. It’s like trying to force a pair of pants to act as a shirt. Can you do it? Possibly. Would it work well? Probably not.

The drawing back of the spine with a torch is a slightly different question as it assumes full quenching rather than edge quenching. I fail to understand how performing a complete transformation to martensite and then differentially tempering a section of it could be “no good”. I’m one of those guys who quenches all of the blade, including the tang, and then draws the tang/ricasso areas back with a torch to create a differential temper. This is fundamentally different from an edge quench that leaves the spine soft, and is absolutely necessary with the modern steels we use in custom knives. (I know tis is widely debated, but that is my opinion)

So what stainless steels are we talking about, and what is their composition?

What are you trying to achieve with the differential HT?