one more time, (this is not for you, but some other folks). Hardness has little to do with machinability. Fine example is a piece of Hestalloy, or better yet 349 stainless steel. The stainless steel will be well under 12 points RC, but go out there and start cutting it. Ampco bronze cuts like butter if you got your stuff right, but one slip up will eat your tooling alive. So what's the difference? Start off with nickel, and just for the fun of it add a little chrome.
By the way a chunk of Hestalloy will reduce a ABEC 7 or 9 grade bearing set to a grade three in about a half hour if things are not well over built
gary
And what do they say about opinions?