blade quenching fact or fiction

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dogwood dan

dogwood dan

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I have ben doing some reading and have heard the grate virtues of "blade quenching" mostly from old text or classically trained smiths. for the purpose of this question I am defining blade quenching as to place the blade tip to recusso edge down in a quenchent but not submerging the full blade. The purpose of this is to get a varied hardnesses throw the blade, the desired effect of this varied tempering is to get a keen edge and a flexible spine.


this weekend at a hammer in I saw several blade smiths that I greatly respect not using the practice, nor have I seen it in shops that I have visited. Is it out of date, impractical, a myth or something i need to be studying?
 
The method one chooses to quench a blade is based on the desired results. If you are looking for a hardened edge with a softer spine edge quenching is one way to achieve it. You can also quench the entire blade, then "draw" the spine with a torch. To achieve the same end result, you can apply clay to the spine and quench the entire blade. The results are the same its just the method that is different.

Fred
 
And, the term you are looking for is "edge quenching." All blades get quenched somehow or other.
 
There is no good metallurgical reason to edge quench a blade, but there are several reasons not to. As Fred said, fully harden the blade and draw the temper back on the spine. Flexibility is the same hard or soft, BTW.

I know several old timers will say that they always edge quench their blades and that is fine if they are happy with the results.....but my advise to anyone who asks is the do it the better way.
 
Fred.Rowe said:
The results are the same its just the method that is different.
Click to expand...

I have to humbly disagree, Fred... the results are quite different but the desired effect can appear to be similar. Though, Edge quenching and clay coating are very similar, a full quench and select temper is a very different animal and some would dare to say more "metalurgically sound"...... oops, I guess I said it.

Not that any of these methods are necessarily wrong. It would be a shame to lose those beautiful temperlines that come from differential heat treatment. However, our understanding of modern metallurgy has come a long way.... better steel, better equipment..... better results.




Rick
 
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Ole Dan has brought up a very interesting thought. I edge quench just about all my blades. With the 10XX steel I look for the transition line to show and add to the look of the knife. With 01, 5160, 52100 that line isn't going to show, but the chance of serious warping is reduced. Now, I can fix any warp right out of the quench, so not a problem there. I'd like to hear about the reasons this isn't the way to go. Serious question and one that's meant to make me better. Glad to have you at the hammerin, Dan.
 
I'm asking. Not stating. Isn't the difference between the edge quenched blade and a drawn back blade is that one leaves you with a pearlite back and the other a tempered martensite back?
I'd like to know more of the metalurgical reasoning behind the methods.
 
Brian Ayres said:
I'm asking. Not stating. Isn't the difference between the edge quenched blade and a drawn back blade is that one leaves you with a pearlite back and the other a tempered martensite back?
I'd like to know more of the metalurgical reasoning behind the methods.
Click to expand...
pretty much got that one correct. You get a gold star. Full quench gives you a strong spine that you can control how much toughness you impart to it, edge quench gives you pearlite and mixed structures with all the inherent weakness that entails

-Page
 
Rick Marchand said:
I have to humbly disagree, Fred... the results are quite different but the desired effect can appear to be similar. Though, Edge quenching and clay coating are very similar, a full quench and select temper is a very different animal and some would dare to say more "metalurgically sound"...... oops, I guess I said it.

Not that any of these methods are necessarily wrong. It would be a shame to lose those beautiful temperlines that come from differential heat treatment. However, our understanding of modern metallurgy has come a long way.... better steel, better equipment..... better results.




Rick
Click to expand...

A poor choice of words on my part. Thats the problem with making blanket statements. I do understand the metallurgical differences that result from using the different techniques I mentioned.
I'll select a smaller brush next time:) or expand my statement and give a more concise answer.

Fred
 
bladsmth said:
There is no good metallurgical reason to edge quench a blade, but there are several reasons not to. As Fred said, fully harden the blade and draw the temper back on the spine. Flexibility is the same hard or soft, BTW.

I know several old timers will say that they always edge quench their blades and that is fine if they are happy with the results.....but my advise to anyone who asks is the do it the better way.
Click to expand...


i am new to metal working (my back ground is in wood working) but my understanding was the harder the metal the more brittle it is, I thought that is why springs are tempered to a med 40's on the rc scale while a knife blade/ edge is in the hight 50's?
 
That's true. So, a blade that may be Rc 59 at the edge, and spring tempered at the back, will be more flexible and tough than one with a full hardness of Rc 59. It will also be stiffer than a knife with a pearlite spine.

My thinking is that full quench with soft back draw is the way to go, as well.

Some fellows will tell you otherwise, a few of whom are really good smiths.
 
I won't go into a long metallurgy paper here, but differentially tempered martensite is going to make a more reliable blade than two different structures. If you have bricks and mortar, where do you think the wall will break?

I am not saying that a differentially hardened blade is a bad blade, just that there are metallurgical reasons to have one structure, not two.

Flexibility is related to the material and the thickness. The point where it breaks or takes a permanent bend is related to the hardness and temper. A Rc 45 spring has the ability to return to shape with more flex than a Rc 62 blade. They both will flex with the same amount of force. It is all part of a complicated thing called the modulus of elasticity.

If you are seeking a hamon, or quench line, all that is based on aesthetics, and not metallurgy.
 
It would be very easy to get into a great debate on this subject, but I will simply suggest that you do as I did and try various methods, test the knives to destruction and see for your self which works for you and the kind of knives you want to make.
 
I believe it is the responsibility of every professional knifemaker to be well educated in whichever method they use. With that should come the burden of seeking to understand the methods you don't use... it only makes sense. Still, many good smiths have fallen short in this regard and seem content to work within such limiting parameters.
 
Personally I prefer the edge quench. I never could get repeatable results draw tempering the back, some would be springier than others. With the edge quench I get exactly the stiffness I want. I also quench most of my blades a bit higher up the blade than a lot of the edge quenched blades I see. More than one way to skin a cat, just the way I do it and it works for me.
 
Should you want to know what I do and why there is a long thread on this form where Dan Winkler and I discuss my methods, he asks questions and I answer him, it provides the most involved discussion in one place on what we (my team) and I have learned over the last 30 years or so. I don't know how to post a link to it, maybe someone else will post it for me.

Will52100 just provided a good reason for the edge quench, right in line with what we have found.

In my experience you can spend a life time learning one steel well. In learning that steel you will know what works and what does not work and why.

The most critical aspect of the quality of a knife makers education can come from his personal methods of testing his blades doing the work he intends them to do. You have everything in your shop to test the performance qualities of your blades.

When a knife maker gives you advice or criticizes another makers methods, just ask him how he tests the performance of his blades and if he can explain it in simple to understand terms that you can understand he may know what he is doing.
 
Rick Marchand said:
more "metalurgically sound"..... Rick
Click to expand...

What's that mean Rick?

It's the same metallurgy, just different logic and reasoning behind the two. There is only one type of metallurgy,... "human metallurgy". I agree that the most important thing is to understand both types of quenches and logic, and then apply whatever reasoning you like to it.

However,... I do think a full quench will make a better pry bar. :)
 
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