With 1084 I have been doing some testing. So far I found I like 61hrc-62hrc for anything but a big chopper/camp knife. A big chopper I have been likening 59hrc-60hrc. But all this is subjective to edge geometry and also the tools you have in your shop. I am just a hobbyist knifemaker so take what I say with a grain of salt. The only thing I can really suggest is to do a lot of testing and see what you like.

I can see no reason to intentionally blue the spine of a hunting knife. I prefer mine full hard, if I did, in fact, austenize the entire blade. Fully hardened and tempered martensite is much stronger and tougher than "softened" steel. (Think about a fillet knife. It's fully hardened yet the geometry allows it to flex and return straight. If it had an intentionally softened spine it would stay bent.)

With shallow hardening steels like we mostly use, many of our thicker areas do not get fully hardened, anyway.

I would not want mine to somehow take a severe bend and set that way.

On hunting knives I mostly go for full hard of the entire blade. Double temper at 415+/- and test a bit. Most generally they're good to go.

For higher carbon steel like W2 I temper about 30 degrees higher and test. But I still go for full blade hardness.

Jason, Karl,

Thank you for your replies. I realized I had an omission in my original post, in my examples I meant to say a 5" kitchen utility knife from 15N20.

But I also realized I may not have asked my question clearly. There is a relationship between the steel type, heat treatment, and final properties. A hypereutectoid steel might perform better at a higher hardness than a hypoeutectoid steel, and vice versa, thus making one a better choice than the other for a particular knife. But I was looking at it from the starting point of the knife. If one wanted to build a particular kind of knife (hunting, chef's, slicing, chopping, ??) what hardness should it be? Then a steel can be selected that will give the proper hardness (and other properties) needed.

I know it is a chicken and egg type of thing. I'm wondering what makers do as far as knowing what knife they want to build, and then considering the requirements for that knife to select the steel. I suppose sometimes people might look at something in their inventory and think about what they can make with it, but I am guessing most people first decide what they want to make (maybe from a customer request), and then select the steel based on the requirements. Thus I am looking for opinions, for different knives, about what the hardness should be (and therefore what steel would be a good choice to achieve that hardness). I hope this helps.

Karl - Thanks also for your comments on bluing the spine, it makes a lot of sense.

Thanks,

Dave

My suggestion would be to test the knives in their usage range.

Hardness is only part of the equation.

If your knife performs as you wish/expect ; carry on.

If it fails in some way address that part of your test.

Several factors are in play at any hardness range.

Check this article out How to pick the best steel for every knife

Jason,

Good article, thanks. There are also links to other related topics in the article.

Mike - Thank you. I am aware hardness is only part of the equation. The reason I singled out hardness in my question is because it is an important parameter which can be easily measured in a non-destructive fashion (if done on the tang under the handle or guard) on every blade. This makes it a good quality assurance parameter. If there are simple non-destructive test which can be done on every blade for other key parameters (e.g. toughness) I'd be very interested in learning about them!

Thanks,

Dave

David,

For years now the ABS has encouraged testing every aspect of a knife's behavior. And this is really what you are asking about, it's behavior. In other words, how does this "parameter" and it's set point affect the behavior of that knife compared to it's intended usage?

The fact is that you must have a failing point to know where to set your parameters for every aspect of it's behavior. As Mike said above, this requires testing. This testing may actually damage the blade to where you shouldn't try to salvage it, but it is worth knowing the information gained from the test. Then you can stop short of destruction on your regular run of blades of that type, steel, heat treat, etc.

There are variables from shop to shop that are often overlooked when in such discussions. But the process that would end up with a well performing blade is certainly available to about anyone.

By the way, a simple non destructive test that will test the actual edge is to use a file. From that point you can cut and chop till the edge takes damage and you know it's limits.

Test, test, and test.

To add another layer to the "parameters"..... something that many newer Bladesmiths/Knifemakers fail to consider, is the customer's ability/ease of resharpening a blade. It doesn't matter the blade material, or how hard it is, sooner or later any blade will go dull with use, and require sharpening. One of many questions to consider as a Bladesmith/Knifemaker is..... How easy, or difficult will it be for a client to sharpen a knife I produce for them??

The higher the hardness level, the more difficult it is for the average knife owner to sharpen, and in my experience, the more frustrated a client becomes with the knifemaker. Personally, for the steels I use, and the geometries I apply, I shoot for a finished Rc 57-59 for most blades..... on the low side for larger blades, and on the higher side for smaller ones. As a Bladesmith/Knifemaker, don't let yourself get fixated on high hardness... there's more down sides to it than you likely realize. It's all about balance..... it's gotta hold an edge, but it also needs durability, and MUST be relatively easy for a client to maintain.

That's the tightrope every Bladesmith/Knifemaker walks....and if you don't find yourself doing so with each knife you build.....you're missing the mark.

Lin,

Thank you for putting this in perspective. I can see that I need to expand my testing and also test on a more regular basis.

Thanks,

Dave

Ed,

Thank you. I guess I am hitting the mark, or coming close, because that is exactly what concerns me! I'm not necessarily trying to make harder blades, but get concerned that my blades should be harder. As a knife user for 50+ years I am in the tough and easy to sharpen camp, but as a new knife maker I am not sure that is where I should be. Your comments provide some assurance that I am headed in a reasonable direction.

Thanks,

Dave

|quoted:

My suggestion would be to test the knives in their usage range.

Hardness is only part of the equation.

If your knife performs as you wish/expect ; carry on.

If it fails in some way address that part of your test.

Several factors are in play at any hardness range.

Well said! Plus one.