Testing the hardness of vintage steel

I enjoy watching Forged In Fire and I see the makers testing their blades with a file after the quench to check for hardness. But this just seems to tell them if the steel took the quench or not, not the actual hardness they achieved.

Course then they sharpen on a belt sander, so I guess the particular hardness doesn’t matter since they just use them on the couple tests the judges have set up. No long term usage of the knife involved. I’d guess they end up pretty hard. Too hard though and I assume they’d break.

On the old pocket knives I carry from time to time, they seem pretty soft as compared to modern steels, whether carbon or stainless. Based solely on ease and frequency of resharpening.
 
IIRC, I read in another thread recently (might have been an old one I searched up) that current production Case CV will usually test anywhere between 54-58 HRC, and that GEC shoots for 59 HRC with their 1095. My understanding is that the batch hardening methods that Case uses for a large volume of blades produces some variation in hardness. GEC, dealing in smaller quantities, and having blades hardened by Peters, has the luxury of being more specific. At least I think that’s what I read.
 
Ernie1980 said:
I have heard that most makers shot for around 55 or maybe a bit higher, but would love to hear from someone who has tested any!
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The military specification, for certain pocketknives made during WW2, stated the Rockwell hardness (56 -61) to be attained by the manufacturers. I find that to be pretty impressive. After sharpening a large number of them, I'd guess the Camillus blades to be approximately 58. Definitely harder than modern day Case CV. Much closer to current GEC offerings.

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That is neat information Buzz!
Regarding the testing on vintage knives that produced hardness numbers in the 40s, I wonder if this was because they were testing the tang because of the flat area??
 
Joe58 said:
I enjoy watching Forged In Fire and I see the makers testing their blades with a file after the quench to check for hardness. But this just seems to tell them if the steel took the quench or not, not the actual hardness they achieved.

Course then they sharpen on a belt sander, so I guess the particular hardness doesn’t matter since they just use them on the couple tests the judges have set up. No long term usage of the knife involved. I’d guess they end up pretty hard. Too hard though and I assume they’d break.
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I think it worth pointing out that Forged in Fire is a bit misleading in the hardening/tempering process, when you see a contestant quench his/her blade they are hardening it, they are aiming for full hardness of that particular steel, the file skating tells them it's hardened not the actual hardness.
The blade is now too hard to use & will break or shatter if bent or dropped, but can still be ground if kept cool.

The organisers temper the blades before the contestants put handles on, meaning they "bake" them at a controlled temperature/time to bring the hardness down to make the blade usable, otherwise they would be too hard/brittle & could snap/shatter.
This is very rarely mentioned important part of the process, left out no doubt because it's boring but I think it's hugely misleading to the viewers not to make it clearer.

The blades can be ground soft (pre-hardning or tempering), or hard, the only difference being before hardening it doesn't matter if the blade heats up when grinding (it's just been in a forge!), after hardening or tempering any heat above the tempering temperature will soften the blade, so grinding is then performed while keeping the blade relatively cool, bare hands holding the blade are good indicators!

As for sharpening or re-shaping an old bade generally as long as it's kept cool there will be no effect on hardness, not always easy on fine edges & tips, a give away to overheating when grinding is a colour change in the steel.
 
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