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Rockwell testing?

strigamort

February 22, 2013 01:14

Hi guys! I asked over on Bladeforums.com and I believe it was Ryan who suggested that I ask here.

What all is involved in Rockwell testing? Can it be done through a coat of Cerakote and if not is the tang a suitable testing area?

A video of how it's done would be awesome!

Thanks!

Comments

12 comments

strigamort

February 22, 2013 01:18
Oh and just for the sake of clarity, is the hardness on the Contego the same from the first one you made to the now? I had read somewhere that at some point you bumped up the hardness and I've been wondering how to tell if mine is one of the later ones.
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lightning

February 23, 2013 03:23
Watching a Rockwell test is pretty dull (no pun intended).

All it is is seeing how far a hydraulic press can push an 'indenter' into a piece of steel at a certain pressure to see how far it goes in. The deeper the indent, the softer the material. When all is said and done, all you will see is a quite small dent where the test was performed.
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deathofallthings

February 23, 2013 06:24
I've seen it done at a machine shop once... I really thought it was some kind of fancy surface gauge till the guy told me what it was. I don't see any reason you couldn't test on the tang, should be the same hardness as the rest of the blade.

I'm not sure if the coating would affect the hardness reading or not.
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bmkjason

February 26, 2013 00:40
Rockwell testing is essentially pressing an indenter into the steel and measuring the distance it can penetrate the material (as Lightning mentioned above). Testing must be done on a bare surface (no coating) and should also be done away from the edge of the sample, as doing either can compromise the accuracy of the test. You can definitely test on the tang.

The 810 was always produced with CPM-M4, heat treated to 62-64 HRC.

Hope this helps!
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dj

February 26, 2013 03:05
quote:

The 810 was always produced with CPM-M4, heat treated to 62-64 HRC.

It does help .......thank you.
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dj

February 26, 2013 03:05
What was the rockwell on the old M-2 knives ....???
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bmkjason

February 26, 2013 18:11
If I am not mistaken, the hardness range on M2 the last time we produced it was 58-60 HRC.
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archer

February 26, 2013 19:10
quote:

Originally posted by BMK Jason:
If I am not mistaken, the hardness range on M2 the last time we produced it was 58-60 HRC.

Is'nt that the same as 154CM?

The M4 on the Contego is hard, it's evident when trying to sharpen it, it takes longer and you can tell by the amount of residue left on the honing stone.
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bmkjason

February 26, 2013 20:30
quote:

Originally posted by archer:

Is'nt that the same as 154CM?

It is pretty close. 154CM has a range of 58-61 HRC. It can get a little bit harder than M2.
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strigamort

February 27, 2013 14:35
Thank you very much! I am very much enjoying the knife. An excellent model.
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skimo

March 05, 2013 04:07
I think I would contact a company that does heat treating and see if you can get the blade tested, I don't think it would be free or even cheap, but I'm not too sure, worth the phone calls.
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lightning

March 17, 2013 03:36
You have to keep in mind too, that a 60 Rc on one material cannot be directly compared to 60 Rc on a different material.

Each and every material has different mechanical properties at a certain hardness than does another. A perfect Rc for CM154 (for instance), maybe be way too hard and be too brittle for another, or could be way too soft for edge retention.

As I've said a great many times before; Don't compare knives based on the hardness of their blades. Just because one has a higher hardness rating does not mean it's going to perform better. The right hardness can only be determined through empirical testing and will only apply to the specific material being tested.
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