What does this mean...?

GreySteel

GreySteel

Joined
Aug 2, 2008
Messages
135
For example when you look at the specs of knives and how they are made sometimes when you look at the hardness of a blade it has like 60-56 Rc. What does the Rc mean and #-# a ratio of what? Thank you for your time.
 
The numbers indicate the hardness of the steel of the blade in the Rockwell C scale. This is determined with a Rockwell hardness tester where a weighted diamond stylus is dropped onto the steel leaving a little dent which is then measured to determine how hard it is. The deeper and wider the dent, the softer the steel.
Rockwell hardnesses are usually given as two numbers, such as Rc 58/59 or Rc 60/61. This is because determining the exact hardness is very difficult so you can more easily say it's "about 59 to 60 Rockwell" (RC 59/60) far more reliably than you can state that something is exactly 60 Rc.
 
It's the blade hardness, modern steels are expected to be between 56-62 on the Rockwell C scale. The higher the hardness the more brittle the blade, but a harder blade can be made sharper. It's not generally used in knife purchasing decisions, certain steels perform best in a set range. The Rockwell test proves that the steel is in it's nominal range.
 
Basically what everybody else said, you got a lot of good bites real quick :D

You can look around and find out what is the preferred range of Rc for each specific steel. You wouldn't want 440A at something ridiculous like 62 Rc, it's meant to be softer and would probably snap in two if put that brittle.
 
Thank you, all of you for your quick helpful and awesome replies. Really helpful, thank you.
 
Something I am curious about is how to interpret the scale. How much harder is for example an RC of 60 compared to an RC of 59? Is it 1/60 = 1.667% harder? Or since the test is about a volume, is it 1.667 x 1.667 x 1.667 = 4.63% harder? Or is there another relationship?
 
You must log in or register to reply here.
Back
Top