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Is there a simple way to check the heat treatment of a blade?
- Thread starter agony
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Gossman Knives
Edged Toolmaker
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- Apr 9, 2004
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That maybe a difficult question to answer. What factors are you looking for from the heat treat? As you said the best way to see how well a blade is heat treated is by using it. If you want to know the hardness a rockwell tester would be necessary. Not sure but I think a metal fabrication or machine shop may be able to help with that. There are some knifemakers who also have rockwell testers. This a good question for forum member mete to answer. Maybe he'll chime in. 
Scott
Scott
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A simple way ? No.If you are asking to find which of two makers is the better blade that's not simple at all .For your example though, Bob Dozier is considered the master when it comes to heat treating D2.You would have to establish criteria and do a side by side test.
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There are crude tests, but you have to own the knife before you can apply them. One variant is file and wire testing. If you can't hone the edge at all with a new mill bastard file it is "hard" (over 58). If you can cut iron bailing wire without nicking the edge it is tough.
What I use to measure hardness is the feel I get on a hone. I like to measure toughness by chopping on beef rib bones.
If you have two blades you can see if one is hard enough to scratch the other one.
What I use to measure hardness is the feel I get on a hone. I like to measure toughness by chopping on beef rib bones.
If you have two blades you can see if one is hard enough to scratch the other one.
If you are willing to damage or destroy the blade you could section part of it off and put it under a microscope to determine the specific grain structure, which would tell you something about the heat treat if you know what to look for. Of course, for this to be useful you would have to establish what grain structure resulted in a "good" tool for your application.
There are several ways to test the hardness and flexibility of the blades, but this would result in a very incomplete understanding of the tool's properties.
AFAIK there is no real way to check a heat treat without destructive testing, as it is a process rather than a easily identifiable and constant feature such as shape or material.
I've seen a few reviews that people do of a knife that is just recently out of the box and has only been used for a few hours in which they (incorrectly) say something like "this knife seems to have a good heat treat" after cutting some bits of paper and cardboard. This perhaps confuses people into thinking that a heat treat is something that is easy to quantify.
There are several ways to test the hardness and flexibility of the blades, but this would result in a very incomplete understanding of the tool's properties.
AFAIK there is no real way to check a heat treat without destructive testing, as it is a process rather than a easily identifiable and constant feature such as shape or material.
I've seen a few reviews that people do of a knife that is just recently out of the box and has only been used for a few hours in which they (incorrectly) say something like "this knife seems to have a good heat treat" after cutting some bits of paper and cardboard. This perhaps confuses people into thinking that a heat treat is something that is easy to quantify.
In college I worked at a cam-shaft manufaturing plant. The "test" of the heat treat was:
- checking for cracks on a magnaflux
- surviving the after-heat-treat straightening process without snapping or cracking. (heat treat often causes long metal parts to warp)
Both were Pass/Fail situations and while not very scientific, were very practical.
But as many are alluding to, heat treat is what the manufacture intends it to be for a given use. Often times the ideal is varing hardness with the blade edge being hardest of all and the body of the blade being softer. Quenching media plays in this too.
In practical terms, the two you mentioned are about IT unless you are willing to ruin a bunch of blades for the cause of knife science.
But we'll all watch with enthusiasm!
- checking for cracks on a magnaflux
- surviving the after-heat-treat straightening process without snapping or cracking. (heat treat often causes long metal parts to warp)
Both were Pass/Fail situations and while not very scientific, were very practical.
But as many are alluding to, heat treat is what the manufacture intends it to be for a given use. Often times the ideal is varing hardness with the blade edge being hardest of all and the body of the blade being softer. Quenching media plays in this too.
In practical terms, the two you mentioned are about IT unless you are willing to ruin a bunch of blades for the cause of knife science.
But we'll all watch with enthusiasm!
An interesting topic. Although important in a good knife, this is apparently something very difficult to measure. I notice in the Japanese knives/swords the heat teat is often visible. Since the heat treat area is not visible in most production knives I am wondering if some are not heat treated at all.
bell said:
What you see in these Japanese blades is the variation in the crystal structure of the metal from the different treatments (heat and otherwise). I think many of these are actually just a variation in the way the blade is polished in order to simulate that look.
Some very cheap knives without a ground edge might not be, but if it has a ground edge it would have to have *some* treatment or otherwise be incapable of holding an edge for any length of time. It would also be easily bent without showing any or minimal surface cracking.
(I had to take an engineering materials class in college that hit on a lot of this.)
You asked if there is a "simple" way to check heat treat of a blade. And the answer is no "simple" way. The larger knife companies will have a metallurgical lab where they do quality control and use diamond point hardness testers and microscopic exam of grain structure on some sample blades from a lot to verify heat treatment worked. Heat treating these specialty steels is complex, with special quench and temper cycles to get it right, and even sub freezing cooling on some of the steels. Just doing a quench from high temp and nothing else will leave the steel in a brittle condition. Too much tempering, or wrong tempering temperature will soften the blade too much.
However, you can get a fair idea of how one blade compares to another by sharpening the blades the same way on something like an EdgePro rig. Then do some cutting, like on heavy cardboard and see which blade holds the edge best. The steel analysis makes a difference too. Not everybody's D2 is exactly the same.
The file test will tell you a little bit, but I ain't doin no file test on my blades. If you want to try that, use a small triangular file and run one of files edges over the blade. If it don't scratch the blade, then, hey, maybe it wasn't tempered correctly. A file is about RC 59-60. Your knife blade shouldn't be that hard or it will be brittle. And the file should scratch it. If the file scratches too easily, and sorta digs in, then you've got a soft blade.
You can also try what was suggested, use the tip of the blade and try to scratch the blade on the other knife. Then switch places. It may give you and idea which one is the "hardest".
Good luck and let us know if you discover a way.
og
However, you can get a fair idea of how one blade compares to another by sharpening the blades the same way on something like an EdgePro rig. Then do some cutting, like on heavy cardboard and see which blade holds the edge best. The steel analysis makes a difference too. Not everybody's D2 is exactly the same.
The file test will tell you a little bit, but I ain't doin no file test on my blades. If you want to try that, use a small triangular file and run one of files edges over the blade. If it don't scratch the blade, then, hey, maybe it wasn't tempered correctly. A file is about RC 59-60. Your knife blade shouldn't be that hard or it will be brittle. And the file should scratch it. If the file scratches too easily, and sorta digs in, then you've got a soft blade.
You can also try what was suggested, use the tip of the blade and try to scratch the blade on the other knife. Then switch places. It may give you and idea which one is the "hardest".
Good luck and let us know if you discover a way.
og