Hardening Question

[Hunter10139]

So guys I was watching a guy going for his abs mastersmith on youtube and he edge quenched his knife. Watching him made me curious. Is edge quenching a good idea just for larger knives used for chopping, or can it be used on smaller knives? It seems like Its not needed for most knives, but I wanted to ask y'all if any of you use that method and why.

[Doug Lester]

Edge quenching is a good idea for knives for the ABS performance test. It might be good for larger knives meant for heavy chopping but little use, at least in my opinion, for smaller knives. What you are doing is trading some strength for toughness in the spine when you differentially harden a blade as with edge quenching. Whether that is good or bad or useful or not useful is going to depend on the overall design of the blade and the exact use the blade is put too. There's a big difference between using the blade to cut heavy brush and using it as a substitute for an ax to cut small trees and limbs.

Doug

[Ray Rogers]

Edge quenching can be used on smaller knives but, as Doug pointed out, isn't likely to be very useful on most small knives. Eli Jensen edge quenches most of his little knives so that he can get a temper line to show on his blades - strictly decorative.

If done incorrectly, edge quenching can weaken a blade by creating an area along the quench line that is more prone to cracking than we would find acceptable. This is the result of having too wide a differential between the hard and soft parts of the blade.

Bottom line: edge quenching (or clay coating) can add toughness to a blade, even a small blade, but before deciding to do your HT that way it is prudent to consider whether or not the already extreme toughness of any good blade steel with a proper full quench will be enough toughness for that particular knife ...

[Hunter10139]

Ok thanks for the responses that answers my question

[jmccustomknives]

I've got a slightly different perspective, and result. I do edge quench most of my knives. Mostly because I want a nearly unbreakable blade but the trade off is a soft spine. A gentleman whom I made a small knife managed to put some dings from hammering on the back of his knife. That's the trade off. I think the softback draw is a better method if you don't need or want the temper line as you can take the spine to a spring temper rather than the softer annealed state.

[sdcb27]

Hunter, The reason he edge quenched had nothing to do with how tough the knife might be but to pass the test which is a admittedly flawed test as best

[Crex]

Lot of truth in what has been said above on most counts.
Actually on most smaller and thinner blades, dependent on the steel(s) used, probably won't make that big a difference as most will harden pretty much to whole blade anyway.
Doug and Romey are correct on the video being about a certain process for testing and not necessarily a good process for quality cutlery.
Lot of stuff out there that can lead you down wrong paths....you must read/process with care and use educated discernment.

[Ed Caffrey]

I'm gona go the other direction of most replies.....personally I like the "edge quench", and do a lot of it. The reason I like it so much is that it gives me MUCH more contral over the characteristics of the finished product versus a completely hardened blade. I can make a blade limber of stiff, soft or hard, and a number of other characteristics that can enhance usability beyond what I can get with a fully hardened blade. When done correctly, cutting ability certainly isn't degraded, and in many cases it's better then a fully hardened blade.
It's all based on whether an indivdual is willing to put in the time and effort to experiement, and nail down a process that achieves the results desired.

[Hunter10139]

Ok guys then how much of the edge do you quench? I assume that a too large amount would render the soft back pointless and with too little a user might wear the hardened edge off. Would a ratio like maybe 1/3 the width of the blade be something ok or is there more too it.

[Ed Caffrey]

Ok guys then how much of the edge do you quench

That's one of the keys that many don't consider, and just approximate. The standard answer is 1/3-1/2 of the blade's width.

BUT....... this is exactly what I was talking about when I posted my reply....it's not just about how much of the blade's width is hardened....it also depends on the type of steel, the grind geometry, and even if the blade has distal tapers or not. That's why I made the statement about putting in the time and effort to get all the variables right for YOUR BLADE(s). There is no "exact" answer... it can vary from blade to balde, and individual to individual.

Let's use the aformentioned "ABS test blade" as an example.... a person who knows what they're doing would harden as little of the edge as possible, and still be capable of passing the chopping portion of the test, while ensuring that the majority of the blade was soft, in order to ensure it would meet the 90 degree bend requirement. How much is that? For my JS test blade is was approx. 1/3 of the blade's width.....for my MS test blade, it was a little less then 3/8" of the edge.

Now, were I building a similar style blade for let's say daily camping chores, I'd harden about 3/4 of the blade's width, which would give me a much stiffer blade, but still one that would not shatter into pieces if I put too much stress on it. I'd likely also make the grind geometry slightly heavier then I would for a "test" blade.

Controlling key characteristics is the actual test that the ABS lays out....not the overall blade/knife. Some makers will never grasp it, and for others like me, it was a great epiffiany when I realized how much control I could have over the end product.