Recoil Rob,



To begin with the "B" scale and the "C" scale are completely different measurements using completely different systems.



The "C" scale uses a diamond cone indenter (brale) and a major load of 150 kg force. It is useful for hardened steels and them the more exotic hard stuff, like carbides.



The "B" scale uses a hardened steel ball (typically although I have heard of carbide balls being used) of 0.0625" diameter and a major load of 100 kg force. It is useful for annealed/normalized steels, brass, bronze, etc, etc.



There isn't any overlap between the "C" and "B" scales that I am aware of.



Basically, the "C" scale begins where the "B" scale ends. So a "B" of "98" would be approximately equal to a "C" of 20.



By the way, from Alf's article the lowest hardness if Rockwell B 77, which would have an approximate tensile ultimate strength of 71,000 psi. The approximate endurance limit for this material would be 35,000 psi.



With most of the Mausers in the article having ultimate tensile strengths greater than 80,000 psi. This is a tad bit better than you average SAE1020 normalized, which runs around 50,000 psi (IIRC). Today's modern actions with SAE4140 chrome moly material @ Rc 32 will have a ultimate tensile strength of 167,000 psi. Of course there are better materials available than SAE 4140, though.



The Mauser's in Alf's article run between BHN of 142 (Rb 77) to BHN 444 (Rc 47). BHN = Brinell Hardness Number by the way.



I personally prefer the Vickers tester to the Rockwell.



ASS_CLOWN

Infosponge,

Thank you for posting the chart. It differs slightly from mine, which was published way back in 1974. As they both say, the conversions are APPROXIMATE.

Mine was from Avner's "Introduction to Physical Metallurgy".

ASS_CLOWN