Arnold,
I can't recall what we discussed, but I looked in my Machinery Handbook and it provided at least 2 options. But it was less detailed than needed to be helpful. So, I googled the question and came up with a link you might find informative.
http://www.wilsoninstruments.com/products/rockwell/rockwell_scale_guide.aspx

I'm thinking someone recommended either the 15 or 30 N scale.

I'm not sufficiently knowledgeable to discuss whether there's a concern of over carburizing or what effects it can have. But, the Wilson Rockwell site does mention deep casehardening use of the RC scale.

Last edited by Chuck H; 08/27/07 06:29 PM.