On Tuesday, November 29, 2016 at 10:12:54 PM UTC-5, wrote:

snip

BTW, traditionally, dead centers are hardened only for the last 1/4 inch or so. All of mine are, and they're 60 years old or more. The hardening leaves a distinctively different color to the steel -- the result is a cone 1/4" long on the very end -- so it's easy to tell when one is a hardened center or not.

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Ed Huntress