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- Mar 22, 2014
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The HRC is the acutal hardness.So is an HRC of 51 2% harder than one of 50? See this is why I’m confused. Sure the bottom line is does the edge do what you want, but I’d like to understand the relationship between the HRC number and the actual hardness. And consequently what a difference between say 59 and 62 means in the case of m390.
Hardness is a component for edge performance.
You're wanting to know apply the HRC to actual edge performance in some type of calculation.
Larrin had made a regression formula from over a decade of CATRA test data to predict CATRA cut testing numbers using plug in values for edge angle, hardness and Carbide volume also with coefficients for carbide hardness.
Here is the formula for M390
-157+15.8*HRC-17.8*Inclusive edge angle+14.6*17.5% CrV7C3 carbides+26.2*2.5% MC type Carbides
So if we have
M390 at 50hrc
That would look like this
-157+15.8(50hrc)-17.8(30°inclusive)+14.6(17.5%CrV7c3)+26.2(2.5% VC)
= 420mm of predicted Total Cards Cut (TCC) in CATRA.
+1 HRC difference to 51hrc plugged into the same formula shows
=435mm TCC
For further explanation this is a 3 part series of articles here.
https://knifesteelnerds.com/2018/11/19/steel-edge-retention/